Laundering apparatus, method of operating a laundry machine, control system for an electronically commutated motor, method of operating an electronically commutated motor, and circuit

ABSTRACT

A circuit for controlling the energization of an electrical load from an AC source. The circuit has a pair of DC lines, and means is provided for rectifying the AC output of the source to apply a DC voltage across the DC lines in the form of a full wave rectified sinusoidal signal. Signal switching means for connection between the DC lines and the load establishes a conductive path therebetween during a variable time interval when the voltage applied by the full wave rectified sinusoidal signal exceeds the voltage across the load, and means including the switching means is provided for chopping the full wave rectified sinusoidal signal to apply pulses to the load during the variable time interval at a frequency which is high with respect to the frequency of the signal. Means connected to the chopping means for modulating the width of the pulses is responsive to an externally derived signal representative of the desired operation of the load, and means is responsive to the load current for modifying the externally derived signal to maintain the amplitude of the load current below a predetermined level whereby a high power factor is presented to the AC source during a predetermined range of operation of the load. 
     A method of operating an electronically commutated motor is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a divisionof copending parent application Ser. No. 141,267 (now abandoned) filedApr. 17, 1980 which was a continuation-in-part of copending applicationSer. No. 077,656 filed Sept. 21, 1979 now abandoned which was in turn acontinuation-in-part of the then copending Ser. No. 802,484 filed June1, 1977. Now U.S. Pat. No. 4,169,990 issued Oct. 2, 1979. In turn,application Ser. No. 802,484 was a continuation-in-part of the thencopending application Ser. No. 729,761 filed Oct. 5, 1976 (nowabandoned), and such abandoned application was a continuation-in-part ofthe then copending application Ser. No. 482,409 filed June 24, 1974 (nowU.S. Pat. No. 4,005,347). All of the aforementioned applications arerespectively incorporated by reference herein. The followingapplications are also respectively incorporated by reference herein:David M. Erdman and Harold B. Harms, Ser. No. 141,268 filed Apr. 17,1980 (now U.S. Pat. No. 4,390,826 issued June 28, 1983); and Doran D.Hershberger, Ser. No. 077,784 filed Sept. 21, 1979 now U.S. Pat. No.4,327,302 issued Apr. 27, 1982. FIELD OF THE INVENTION

The present invention relates in general to a laundering system,including apparatus and method for operating a laundry machine by meansof an electronically commutated motor which provides the basic motion ofthe rotatable laundry machine components.

BACKGROUND OF THE INVENTION

Many conventional laundry machines used a complex mechanism whichadapted a constant speed motor, e.g., one which runs at 1800 RPM, to thecomparatively slow back-and-forth motion of an agitator during a washcycle. The same mechanism adapted the motor to a unidirectional spincycle during which a tub rotated, alone or together with the agitator,at a speed which may have been on the order of 600 RPM. In general, thephysical dimensions of the motor required for such machines, as well asthe dimensions of a transmission for coupling the motor to the machine,may be large and may necessitate that the motor be positioned aconsiderable distance out of line with the axis of the drive shaft ofthe laundry machine. This distance was sufficiently large to accommodatean intermediate belt transmission, as well as whatever gearing wasrequired to step down the speed of the motor. Further, a transmissionclutch was provided to uncouple the machine from the motor whenever theagitator reverses direction during the back-and-forth motion of thelatter.

The above-outlined mechanical arrangement may be unbalanced so thatspecial measures may be necessary to restore the balance of the machine.Further, because of severe demands made on such machine, particularly onthe transmission during a reversal of direction, at least some of suchmachines may have had a relatively short life. It is believed that theabove discussed factors might find expression in high initial cost ofsuch machines, as well as in high maintenance costs and the necessityfor frequent replacement of component parts of such machines.

The transmission for the unidirectional motor required to meet thedemands of such a laundry machine consequently may have a relativelylarge moment of inertia. Additionally, the gear transmission ratiosrequired by the relatively high torque requirements, particularly duringagitator reversal, may have further aggravated this condition. Also, therequirement for dissipating energy whenever the agitator reverseddirections during the wash cycle may have produced inefficiencies. It isbelieved that the greater the inertia of the system, the lower is theefficiency of system operation. Thus, the initial cost of a motor of thesize required for a conventional laundry machine, as well as the cost ofoperation of such a motor, may be high.

Finally, the range of operations of conventional laundry machines isbelieved to be, by necessity, limited. To provide such machines with thecapability of handling a larger number of different laundry conditions,such as may be presented by a variety of present day fabrics and washloads, is believed to materially increase the complexity of thetransmission as well as the overall cost of the machine. Thus, thecapability of such conventional laundry machines may represent acompromise between different expected laundry conditions, modified bycost and mechanical considerations. It is believed that this capability,selected at the manufacturing site and once determined, may be changedonly with difficulty and at great expense. For practical purposes, it isbelieved that no changes were possible once the machine leaves thefactory.

SUMMARY OF THE INVENTION

Among the several objects of the present invention may be noted theprovision of an improved method of operating an electronicallycommutated motor (ECM) and an improved circuit which overcome at leastsome of the above discussed disadvantageous or undesirable features ofthe prior art; the provision of such improved method, and circuit inwhich a plurality of different control functions may be imposed on suchmotor so as to control the operation thereof to provide the basic motionof such apparatus and motor; the provision of such improved method, andcircuit which achieves improved energy efficiency and corresponding costsavings; the provision of such improved method and circuit which may beadapted to a large number of different laundry modes or conditions; theprovision of such improved method and circuit which adapt automaticallyto existing load conditions; and the provision of such improved method,and circuit having components which are simple in design, economicallymanufactured and easily assembled. These as well as other objects andadvantageous features will be in part pointed out and in part apparenthereinafter.

In general, a system is provided in one form of the invention forcontrolling the energization of an electronically commutated DC motorincluding a stationary assembly having a plurality of winding stages,and a rotatable assembly arranged generally in magnetic couplingrelation with the stationary assembly upon the energization of the motorand adapted to be coupled to a load. The system has means for providinga voltage representative of a preselected angular velocity for therotatable assembly and means for providing a voltage representative ofthe actual angular velocity of the rotatable assembly. Regulation meansincludes means for comparing the voltages respectively representative ofthe preselected and actual angular velocities to provide a first errorsignal, and means is responsive to at least the first error signal forproviding a regulation signal. Signal switching means includes a firstinput, an output, and a control input, and means is provided forapplying a full wave rectified sinusoidal signal to the first input.Means is also provided for applying the regulation signal to the controlinput so as to control the duration of the full wave rectifiedsinusoidal signal at the output of the signal switching devices, andfilter means for connection between the output and the signal switchingmeans and the winding stages provides an effective voltage to thewinding stages having an amplitude which varies with the controlledduration of the full wave rectified sinusoidal signal at the output ofthe signal switching means. Means is responsive to the angular positionof the rotatable assembly for providing a position signal, andcommutation means is responsive to the position signal for applying theeffective voltage in sequence to respective ones of the winding stagesthereby to effect rotation of the rotatable assembly generally at thepreselected angular velocity therefor.

In general, and in a method form of the invention, a method of operatinga DC motor energized from an AC source includes rectifying the output ofthe AC source to provide a full wave rectified sinusoidal voltage. Thefull wave rectified sinusoidal voltage is converted into voltage pulseshaving a high frequency with respect to the frequency of the full waverectified sinusoidal voltage so as to provide an effective voltage tothe motor. The voltage pulses are limited to the time interval in eachhalf cycle of the full wave rectified sinusoidal voltage during whichthe full wave rectified sinusoidal voltage exceeds the effectivevoltage.

Generally, and in another method form of the invention, a method ofoperating an electronically commutated motor energized from an AC sourceand having a stationary assembly including a plurality of winding stagesadapted to be selectively commutated, and rotatable means associatedwith the stationary assembly in selective magnetic coupling relationwith the winding stages, the motor being responsive to a control circuitfor controlling the current flow through a plurality of current pathseach including at least one of the winding stages, includes rectifyingthe AC voltage of the source to provide a full wave rectified sinusoidalvoltage. Pulses are generated having a high frequency with respect tothe frequency of the full wave rectified sinusoidal voltage. The windingstages are commutated by applying the full wave rectified sinusoidalvoltage thereto and causing the current paths to become conductive in atleast one preselected sequence. The conductivity of respective currentpaths is controlled as a function of the width of the pulses when thecurrent paths are sequentially rendered conductive.

In general, and in another form of the invention, a circuit forcontrolling the energization of an electrical load from an AC sourceincludes a pair of DC lines and a circuit for rectifying the AC outputof the source to apply a DC voltage across the DC lines in the form of afull wave rectified sinusoidal voltage. The controlling circuit also hasa circuit for chopping the full wave rectified sinusoidal voltage toapply pulses to the load at a frequency which is high with respect tothe frequency of the full wave rectified sinusoidal voltage during thetime interval when the full wave rectified sinusoidal voltage exceedsthe voltage acrosss the load. A further circuit is connected to thechopping circuit for modulating the width of the pulses and for therebymaintaining the amplitude of the load current below a predeterminedlevel responsive to an externally derived signal representative of thedesired operation of the load.

In general, and in yet another form of the invention, a circuit forcontrolling the energization of an electronically commutated motor froman AC source, the motor including a stationary assembly having aplurality of winding stages associated therewith and adapted to beselectively commutated, and rotatable means associated with thestationary assembly in selective magnetic coupling relation with thewinding stages, includes a pair of DC lines and a circuit for rectifyingthe AC output of the source to apply a DC voltage across the DC lines inthe form of a full wave rectified sinusoidal voltage. Also included area circuit responsive to the angular position of the rotatable assemblyfor deriving commutation signals, and a plurality of current pathsconnected across the DC lines each including electronic commutationmeans for connection in series with at least one of the winding stagesand responsive to the commutation signals to render the current pathsconductive in sequence. A further circuit is connected to thecommutation means for chopping the full wave rectified sinusoidalvoltage in each of the conductive current paths so as to provide pulsesin the conductive current paths having a frequency which is high withrespect to the frequency of the full wave rectified sinusoidal voltageduring the time interval when the full wave rectified sinusoidal voltageexceeds the voltage across the electronically commutated motor. A yetfurther circuit is responsive to an externally derived signalrepresentative of the desired operation of the motor for modulating thewidth of the pulses.

Generally, a still further form of the invention is a circuit forcontrolling an electronically commutated motor for use with a powersupply for supplying a full wave rectified sinusoidal voltage, theelectronically commutated motor including a stationary assembly having aplurality of winding stages adapted to be selectively commutated, androtatable means associated with the stationary assembly in selectivemagnetic coupling relation with the winding stages. The controllingcircuit includes a circuit for producing pulses of the full waverectified sinusoidal voltage during a single continuous interval in eachhalf cycle of the full wave rectified sinusoidal voltage and applyingthem to the winding stages in at least one preselected sequence therebyto commutate the winding stages and rotate the rotatable means, thevoltage pulses having a frequency which is high with respect to thefrequency of the full wave rectified sinusoidal voltage. Furtherincluded is a circuit for width modulating the voltage pulses to producesubstantially rectangular current pulses flowing in the electronicallycommutated motor, each of the rectangular current pulses occurringduring the single continuous interval in each half cycle of the fullwave rectified sinusoidal voltage.

Generally, an additional form of the invention is an electronicallycommutated motor system including an electronically commutated motorwith a stationary assembly having a plurality of winding stagesassociated therewith adapted to be selectively commutated, and rotatablemeans associated with the stationary assembly in selective magneticcoupling relation with the winding stages. Also included is a powersupply for supplying a full wave rectified sinusoidal voltage. Thesystem further includes a circuit for producing pulses of the full waverectified sinusoidal voltage during a single continuous interval in eachhalf cycle of the full wave rectified sinusoidal voltage and applyingthem to the winding stages in at least one preselected sequence therebyto commutate the winding stages and rotate the rotatable means, thevoltage pulses having a frequency which is high with respect to thefrequency of the full wave rectified sinusoidal voltage. Still furtherincluded is a circuit for width modulating the voltage pulses to producesubstantially rectangular current pulses flowing in the electronicallycommutated motor, each of the rectangular current pulses occurringduring the single continuous interval in each half cycle of the fullwave rectified sinusoidal voltage.

Generally, a further additional form of the invention is laundryapparatus including means operable generally in a laundering mode foragitating fluid and fabrics to be laundered therein and operablegenerally in a spin mode for thereafter spinning the fabrics to effectcentrifugal displacement of fluid from the fabrics, and anelectronically commutated motor with a stationary assembly, amulti-stage winding arrangement associated with the stationary assemblyand having a plurality of winding stages adapted to be commutated in aplurality of preselected sequences, and rotatable means rotatablyassociated with the stationary assembly and arranged in selectivemagnetic coupling relation with the winding stages for driving theagitating and spinning means in the laundering mode operation and in thespin mode operation thereof upon the commutation of the winding stages.Also included is a power supply for supplying a full wave rectifiedsinusoidal voltage. The laundry apparatus further includes a circuit forproducing pulses of the full wave rectified sinusoidal voltage during asingle continuous interval in each half cycle of the full wave rectifiedsinusoidal voltage, for applying them to the winding stages in one ofthe preselected sequences to commutate the winding stages and effect thespin mode operation of the agitating and spinning means and for applyingthe voltage pulses to the winding stages in both the one preselectedsequence and another preselected sequence to effect the laundering modeoperation of the agitating and spinning means, the voltage pulses havinga frequency which is high with respect to the frequency of the full waverectified sinusoidal voltage. Still further included is a circuit forwidth modulating the voltage pulses to produce substantially rectangularcurrent pulses flowing in the electronically commutated motor, each ofthe rectangular current pulses occurring during the single continuousinterval in each half cycle of the full wave rectified sinusoidalvoltage.

In general, an even further method form of the invention is a method ofoperating a system having an electronically commutated motor including astationary assembly having a plurality of winding stages adapted to beselectively commutated, and rotatable means associated with thestationary assembly in selective magnetic coupling relation with thewinding stages, a power supply for supplying a full wave rectifiedsinusoidal voltage, and a circuit for commutating the winding stages byapplying a voltage thereto in at least one preselected sequence duringsuccessive commutation periods thereby to rotate the rotatable means.The method includes switching the full wave rectified sinusoidal voltageat a frequency which is high with respect to the frequency of the fullwave rectified sinusoidal voltage during a single continuous interval ineach half cycle of the full wave rectified sinusoidal voltage thereby toproduce the voltage applied by the commutating circuit in pulses. Theswitching is width modulated to width modulate the voltage pulses and toproduce substantially rectangular current pulses flowing in theelectronically commutated motor, each such current pulse occurringduring the single continuous interval in each half cycle of the fullwave rectified sinusoidal voltage.

Generally, still another additional method form of the invention is amethod of operating an electronically commutated motor including astationary assembly having a plurality of winding stages adapted to beselectively commutated, and rotatable means associated with thestationary assembly in selective magnetic coupling relation with thewinding stages, the motor being responsive to a control circuit having aplurality of current paths to the winding stages. The method includesrectifying an AC voltage to provide a full wave rectified sinusoidalvoltage and generating pulses having a high frequency with respect tothe frequency of the full wave rectified sinusoidal voltage. The windingstages are commutated by applying a voltage thereto and causing thecurrent paths to become conductive in at least one preselected sequence.The full wave rectified sinusoidal voltage is switched in response tothe high frequency pulses during the time interval in each half cycle ofthe full wave rectified sinusoidal voltage during which the full waverectified sinusoidal voltage exceeds the voltage across the motorthereby to produce the voltage applied by the commutating means inpulses having a frequency which is high with respect to the frequency ofthe full wave rectified sinusoidal voltage.

Still further in general and in one form of the invention, a method isprovided for operating a laundry machine driven by an electronicallycommutated DC motor with the motor being energized by a DC voltageprovided across a pair of DC lines as a full wave rectified sinusoidalsignal derived from an AC source. The laundry machine has a pair ofrotatable components, and the motor has a stationary assembly with aplurality of winding stages and a rotatable assembly adapted to beselectively coupled to at least one of the rotatable components. In thismethod, the full wave rectified sinusoidal signal is converted intovoltage pulses having a frequency which is high with respect to thefrequency of the signal. A first control function is imposed on theoperation of the laundry machine by modulating the width of the voltagepulses in accordance with a selected one of a plurality of firstwaveshapes to provide a resultant effective voltage to the motor, and asecond control function is imposed on the operation of the laundrymachine through the pulse width modulation to selectively set themaximum amplitude of the effective voltage. The voltage pulses arelimited to a variable time interval in each half cycle of the full waverectified sinusoidal signal during which the amplitude of the lastrecited signal exceeds the amplitude of the effective voltage, and thewinding stages are commutated by applying the effective voltage theretoin sequence whereby the first and second control functions jointlydetermine the angular velocity of the at least one rotatable component.

Also, in general, a laundering apparatus in one form of the inventionincludes a laundry machine having a pair of rotatable components; and anelectronically commutated DC motor having a rotatable assembly and astationary assembly with a plurality of winding stages. Means isprovided for selectively coupling the rotatable assembly to at least oneof the rotatable components, and a control system is connected to themotor. Means is provided for applying a DC voltage to the controlsystem, and the control system has first control means including meansfor providing a plurality of first waveshapes, means for selecting oneof the first waveshapes, and means for controlling the application ofthe DC voltage in accordance with the selected first waveshape adaptedto provide a resultant effective voltage to the winding stages, secondcontrol means has means for selectively setting the maximum amplitude ofthe effective voltage through the first control means, and the first andsecond control means are adapted to jointly determine the angularvelocity of the rotatable assembly and of the rotatable componentsselectively coupled thereto. Means for commutating the winding stages byapplying the effective voltage thereto in sequence includes acommutation circuit responsive to the angular position of the rotatableassembly to provide commutation signals, and a plurality of commutationswitching means are each adapted to be connected in series with aseparate one of the winding stages. Means is provided for applying thecommutation signals in sequence to the commutation switching means tocontrol its conductivity, and a first common point is connected to oneterminal of each of the winding stages. First diode means is separatelyconnected between the other terminal of each of the winding stages and asecond common point, and the commutation switching means are adapted tobe connected between a third common point and the other terminal of eachof said winding stages. Means for electrically braking the rotation ofthe rotatable assembly is adapted to apply a negative torque to theassembly and to the rotatable components coupled thereto, and thebraking means include an energy return circuit to connect a variable lowimpedance across the winding stages with the energy return circuitcomprising capacitor means connected between the first and second commonpoints. First impedance means, first transistor means and second diodemeans are connected in series combination between the first and secondcommon points, and voltage divider means and second transistor means areconnected in series combination substantially between the second andthird common points with the voltage divider means including second andthird impedance means connected at a fourth common point. Means isresponsive to the voltage at the fourth common point to control theconductivity of the first transistor means, and means is provided forderiving a control signal representative of the actual angular velocityof the rotatable assembly. Means is provided for applying the controlsignal to the second transistor means to decrease the conductivitythereof whenever the actual angular velocity exceeds the angularvelocity determined by the control means, and the decreased conductivityof the second transistor means is effective to increase the conductivityof the first transistor means. Energy generated upon the commutation ofthe winding stages is stored in the capacitor means for subsequentdissipation, and the negative torque is variably applied to therotatable assembly in proportion to the amount by which the actualangular velocity exceeds the angular velocity determined by the controlmeans.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a laundry machine representative of the existingstate of the art;

FIGS. 2A-2F show various performance characteristics illustrative of thewash cycle of a typical laundry machine;

FIG. 3 is a sectional view of an electronically commutated motor (ECM)that may be used to implement the present invention;

FIG. 4 illustrates an exemplary winding arrangement which may be used bythe stationary assembly of the ECM shown in FIG. 3;

FIG. 5 illustrates a further winding arrangement for the stationaryassembly of an ECM that may be used to implement the present invention;

FIG. 6 is a partially cross-sectional view of a laundry machine inaccordance with the present invention which may be driven by an ECM ofthe type shown in FIGS. 3-5;

FIG. 7 illustrates the angular velocity/torque performance of anexemplary ECM under laundry machine load conditions, using differentgear ratios for the wash and spin cycles;

FIG. 8 illustrates the angular velocity/torque performance of anexemplary ECM under laundry machine load conditions using identical gearratios for the wash and spin cycles;

FIG. 9 illustrates the angular velocity/torque and current/torqueperformance, respectively, of the ECM of FIG. 7;

FIG. 10 illustrates the efficiency/angular velocity characteristic ofthe ECM of FIG.7;

FIG. 11 illustrates the efficiency/torque characteristic of the ECM ofFIG. 7;

FIG. 12 illustrates the angular velocity/torque and current/torqueperformance, respectively, of the ECM of FIG. 8;

FIG. 13 illustrates the efficiency/angular velocity characteristic ofthe ECM of FIG. 8;

FIG. 14 illustrates the efficiency/torque characteristic of the ECM ofFIG. 8;

FIG. 15 is a schematic illustration of a laundering system in accordancewith the present invention;

FIG. 16A shows the essential elements of a control system which usesphase control in accordance with the present invention;

FIG. 16B illustrates the operation of the control system of FIG. 16A;

FIG. 17A shows the essential elements of a control system which usestime ratio control in accordance with the present invention;

FIG. 17B illustrates the operation of the control system of FIG. 17A;

FIG. 18A illustrates a modification of the control system of FIG. 17A;

FIG. 18B shows the relative timing of the commutation signals used inthe operation of the control system of FIG. 18A;

FIG. 18C illustrates the operation of the control system of FIG. 18Aunder various operating conditions;

FIG. 19A shows the essential elements of still another control systemwherein the control functions are performed through the commutationtransistors;

FIG. 19B illustrates the power factor obtained with the control systemof FIG. 19A for a range of operating conditions;

FIG. 20A is a cross-sectional view of an exemplary transmission that maybe used to couple an ECM to a laundry machine;

FIGS. 20B-20D show various cross-sectional views of the apparatus ofFIG. 20A, taken at B--B, C--C, and D--D, respectively, in the latterFigure;

FIG. 21 shows a preferred panel switch arrangement for imposingpertinent control functions on the operation of an ECM-driven laundrymachine in accordance with the present invention;

FIG. 22A shows exemplary waveshapes for selectively controlling theapplied voltage and the current of an ECM in accordance with the presentinvention;

FIG. 22B illustrates a method used for step-sampling a selected one ofthe waveshapes of FIG. 22A, at a chosen rate;

FIG. 23A illustrates a further control capability of the presentinvention for varying the amplitude of the excursions upon oscillationof the rotatable motor assembly;

FIG. 23B illustrates still another control capability of the presentinvention for varying the aceleration of the rotatable motor assembly;

FIG. 24 is a schematic illustration of a control system for an ECMadapted to drive a laundry machine in accordance with the presentinvention;

FIG. 25 illustrates the relationship of pertinent portions of apreferred implementation of a control system shown in detail in FIGS.26-39;

FIG. 26 shows a low voltage power supply for use in the preferredcontrol system;

FIG. 27 shows a rate scaling circuit for use in the preferred controlsystem;

FIG. 28 illustrates a D/A signal converter and error amplifier forcontrolling the voltage applied to the ECM;

FIG. 29 illustrates a D/A signal converter for controlling the ECMcurrent;

FIG. 30 illustrates a phase control circuit using a ramp and pedestaltechnique for controlling the effective motor voltage;

FIG. 31 shows an error amplifier for use in the preferred controlsystem;

FIG. 32 illustrates a circuit for sampling a selected waveshape, e.g., avoltage waveshape, at a variable rate;

FIG. 33 illustrates a circuit for sensing the position of the rotatablemotor assembly;

FIG. 34 illustrates a decoding circuit for providing rotor positioncontrol signals;

FIG. 35 illustrates a decoding circuit for providing commutationsignals;

FIG. 36 shows another low voltage power supply for providing a regulatedreference voltage in accordance with the present invention;

FIG. 37 illustrates another circuit for sampling a selected waveshape,e.g., a current waveshape, at a variable rate;

FIG. 38 illustrates a motor power control circuit;

FIG. 39 illustrates further circuitry and various terminal connectionsof the control system shown in FIGS. 26-38;

FIG. 40A illustrates in flow chart form a preferred mode of operation ofa microcomputer that may be used in the present invention; and

FIG. 40B illustrates a modification of the operation shown by the flowchart of FIG. 40A.

DESCRIPTION OF THE INVENTION

The significance of the present invention in relation to the existingstate of the art will be best understood from a review of the structureand operation of a typical household laundry machine of the type incommon use today, as illustrated in FIG. 1 and designated with thereference numeral 8a. Machine 8a contains, among other components, aperforated tub 10a and a finned agitator 12a, the latter being coaxiallypositioned in the tub. Both components are capable of coupling onto acommon drive shaft, not shown, either for independent movement or forjoint movement therewith. A drive wheel 11 is coupled to the drive shaftthrough gearing 13 and is powered by a drive belt 14. The lattertransmits power from a pulley wheel 16 which is fast with a clutch 18,adapted to selectively engage a constant speed, unidirectional motor 20,e.g. an 1800 RPM induction motor.

The size of motor 20 is determined to a large extent by the torquerequirements placed on it. These requirements are believed to be severesince the motor, although unidirectional, must drive the agitator in aback-and-forth motion. The resultant size of motor 20 and of thetransmission required do not permit placing the motor in line with thedrive shaft of the laundry machine without unduly raising the height ofthe machine. Thus, the motor is placed to one side of the drive shaftand is coupled to the latter through clutch 18, intermediate belt andpulley coupling 16, 14, 11 and gears 13. It is believed that theoff-center placement of the motor not only produces a loss of efficiencybut also unbalances the laundry machine and necessitates that acounterweight 22 be placed diagonally opposite the motor to restore thebalance of the machine.

The operation of the above-described home laundry machine typically hasa wash cycle during which the agitator is moved back and forth through apredetermined displacement angle. The operation further includes a spincycle during which the tub is unidirectionally rotated at apredetermined speed. The wash cycle of such a machine is illustrated inFIGS. 2A-2F. FIG. 2A illustrates the displacement of the agitator in theexample under consideration, from which it can be seen that the agitatorundergoes essentially harmonic motion during the wash cycle. Theequation which describes the displacement of the agitator is as follows:

    θ=θ.sub.0 cos ωt

    θ=1.4 cos ωt

where

θ=Displacement angle in radians

ω=Angular velocity in radians/sec.

As shown in FIG. 2A, in the example under consideration the maximumdisplacement is 1.4 radians. The period of the agitator is 0.6 secondsand the midpoint of the stroke occurs at 0.3 seconds.

The velocity of the agitator during the wash cycle is given by thefollowing equation: ##EQU1## FIG. 2B illustrates the velocitycharacteristic which is seen to reach a peak of 14.65 radians per secondat the 90° and 270° points, respectively, of the agitator travel.

The equation for agitator acceleration is given below: ##EQU2## Theacceleration of the agitator is illustrated in FIG. 2C and is seen toreach a peak of 153.5 rad/sec² at the extremes of the agitator travel.Zero acceleration occurs at the 90° and 270° points, i.e. at the pointsof maximum velocity.

Since the period of agitator oscillation is 0.6 seconds, the agitatoroscillates at a frequency 1.67 cycles/second. The power required toproduce this motion has a double frequency component, as shown in FIG.2D, reaching maximum values at 90° intervals. The equation for derivingthe required power is given below: ##EQU3## where T_(p) =Peak torque

ω_(p) =Peak angular velocity;

K=Constant.

Average power may be approximated by the relationship: ##EQU4## For theexample under consideration, the average power required is assumed to begenerally about 100 watts.

FIG. 2E illustrates the relationship between torque T and angularvelocity ω. As shown, the angular velocity lags the applied torque bythe phase angle β. The derivation of the phase angle is furtherillustrated in FIG. 2F and is seen to be a function of the inertiatorque, i.e. the moment of inertia, and the friction torque, i.e. thefriction factor. The latter is the sum of the friction contributed bythe gears, the agitator and the load in the laundry machine. It does notinclude the friction due to the rotor of the unidirectional drivingmotor, since the rotor does not reverse directions in the laundrymachine under discussion. The lag angle β is approximately 12° in theexample under consideration.

During the spin cycle of the typical laundry machine under discussionhere, the tub is slowly accelerated to a preselected number ofrevolutions, say for instance approximately 300 RPM. At that point aslip clutch maintains constant torque until the water is expelled fromthe tub. The clutch slips at a constant preselected torque. After thewater is drained from the tub, the torque drops below this value and thetub accelerates to its preselected peak speed say for instanceapproximately 600 RPM. It remains at that speed for a predetermined timeinterval, i.e., say for instance several minutes, until all the water isexpelled from the wash load.

Thus, where a constant speed, unidirectional motor is used, a belttransmission and a clutch are believed to be required to provide theoscillating motion of the agitator. Further, gears are employed to matchmotor performance to the desired torque and speed of the agitator. Theclutch is adapted to slip in order to limit the torque applied duringthe spin cycle. Apart from its complexity, it is believed that such amechanism is costly and is subject to frequent breakdowns.

In the present invention, the clutch and belt portions of the aforesaidtransmission are eliminated by a direct drive arrangement for both theagitator and the tub. In lieu of a constant speed induction motor, abidirectional electronically commutated DC motor (EMC) is employed,which is capable of producing the relatively slow agitator oscillationof the wash cycle, as well as the high, unidirectional spin speed of thetub. Both can be implemented by means of appropriate control of thevoltage and current applied to the motor windings.

For a better understanding of the invention which forms the subjectmatter of this application, it will be useful to explain the salientpoints of electronically commutated motors with reference to specificmotor examples that may be used to implement the invention. Typically,the rotatable assembly of the ECM, occasionally referred to herein as arotor, employs means, such as permanent magnets for providing arelatively constant flux field. The stationary assembly of the ECM,sometimes referred to herein as the stator, includes distributed windingstages which are used to provide mutually perpendicular magnetic fieldswhich interact with the flux field to produce rotation of the rotatableassembly without the use of brushes. These winding stages may becommutated on the basis of sensed variables such as, for example, speed,current and/or position of the rotatable assembly. When commutationoccurs on the basis of the latter position, shaft position sensors maybe employed to determine the angular position of the rotatable assemblyat any given instant of time. The sensors may consist of stationaryphotosensitive devices which cooperate with a light interrupting shuttermounted on the rotatable assembly.

In carrying out the present invention, in one form thereby a positiondetecting circuit is used which is responsive to the electromotive forceof the ECM, i.e., to its back EMF. The latter circuit provides asimulated signal indicative of the angular position of the shaft of therotatable assembly. Such an arrangement eliminates the mounting andmaintenance requirements associated with aforementioned shaft positionsensors. A logic circuit responds to these signals and controls currentswitching in the stator winding stages. Means may also be provided forselectively advancing the commutation of the winding stages in order tooptimize motor performance.

FIG. 3 illustrates an electronically commutated motor ECM 10 which maybe used in accordance with the principles of the present invention. FIG.4 illustrates an exemplary winding arrangement for the stationaryassembly of the ECM of FIG. 3. An example of such a motor is disclosedin the above-mentioned patent application Ser. No. 077,784, now U.S.Pat. No. 4,327,302 issued Apr. 17, 1982 incorporated by referenceherein.

A housing 1213 comprises a generally cylindrical sleeve 1219 which maybe formed of any desired material. The sleeve has a bore 1221 extendingtherethrough between a pair of opposite annular end flanges 1223, 1225or the like, integrally formed with the sleeve. A plurality of coolingfins 1227 are integrally formed on sleeve 1219 externally thereofbetween end flanges 1223, 1225, and a plurality of vent holes 1229 maybe provided, if desired, through the sleeve adjacent the end flanges soas to intersect with sleeve bore 1221, respectively. Peripheral portion1187 of stationary assembly 1161 is received within sleeve bore 1221,being retained therein by suitable means.

End shields 1215, 1217 are secured to housing 1213 adjacent opposite endflanges 1223, 1225 of sleeve 1219 by suitable means, such as a pluralityof screws 1231 or the like. A pair of generally centrally locatedbearing openings 1233, 1235 extend through end shields 1215, 1217, and apair of bearing means, such as self-lubricating bearings 1237, 1239 forinstance, are mounted in the openings respectively. Rotatable assembly1151 is generally coaxially arranged within bore 1197 of stationaryassembly 1161 so as to provide a predetermined air gap 1241therebetween. Shaft extensions 1157, 1159 of the rotatable assemblyextend through bearings 1237, 1239 so as to be journaled thereby,respectively. Thus, the pole sections of the rotatable assembly aredisposed in magnetic coupling relation with winding stages a, b and c ofstationary assembly 1161. The winding stages are adapted to becommutated in sequence as discussed hereinafter.

It is characteristic of the stationary assembly under discussion, thatthe number of slots 1165 employed in stationary assembly 1161 toaccommodate a multi-stage winding arrangement 1167 is different than theproduct of an integer multiplied by the number of poles in rotatableassembly 1151. Thus it will be noted that the twenty-six winding slots1165 in the stationary assembly accommodate the three winding stages a,b and c magnetically coupled with the eight poles of rotatable assembly1151. Similarly, the number of slots in the stationary assembly, i.e.,twenty-six slots, is different than the product of an integer multipliedby the eight poles of the rotatable assembly.

In the operation of ECM 30, it is desirable to provide an advancedtiming angle, i.e., an advancement of the energization of commutation ofwinding stages a, b and c, which is defined as angel α. In explanationof this timing angle advancement, zero advancement would occur in ECM 30if one of the winding stages were energized at the instant the magneticcenter of one of the pole sections in the rotor rotated into a positionspaced approximately twenty-two and one-half degrees from the axis ofone of the magnetic poles established by the energization of such awinding stage.

The preferred amount of advancement of timing angle α is associated withthe L/R time constant of multi-stage winding arrangement 1167. At theaforementioned zero advancement, current in winding stages a, b and cwould build up too slowly to achieve maximum possible torque throughoutthe full "on" time. Thus, advancing the commutation angle, as discussedabove, takes advantage of the fact that the generated back EMF is lessduring imcomplete coupling, i.e., when the polar axis of the rotatableassembly and the energized one of winding stages a, b and c are not inexact alignment; therefore, current build-up time and torque developmentcan be improved. If the advanced timing angle is too great, currentovershoots may occur which adversely affect efficiency; therefore, theoptimum value of the advanced timing angle depends to some extent on thedesired speed at which electronically commutated motor 30 is operatedand the torque desired therefor.

With continued reference to FIGS. 3 and 4, the stationary assembly has agenerally cylindrically shaped peripheral portion or section 1187interposed between opposite end 1189, 1191 thereof. However, it iscontemplated that other stationary assemblies having various othershapes, such as opposite peripheral flats thereon for instance, as wellas other slot shapes or configurations, may be utilized within the scopeof the invention so as to meet at least some of the objects thereof.

A plurality of teeth 1193 are integrally formed on stationary assembly1161 between adjacent ones of winding slots 1165, with the teeth andslots extending generally axially through the core so as to intersectwith the aforesaid opposite end faces. The teeth have generallyarcuately spaced apart tips or radially inner ends 1195 which define, atleast in part, a bore 1197 extending generally axially through the corebetween the opposite end faces thereof, respectively. While twenty-sixwinding slots 1165 are shown in the drawings , it is contemplated thatother stationary assemblies having more or fewer winding slots may beemployed or that winding slots of various other shapes may be used.Furthermore, while teeth 1193 and tips 1195 thereof are illustratedherein as being generally radially extending or straight, it iscontemplated that teeth and tips thereof having various other shapes orpositions may be employed.

The winding arrangement used is best shown in FIG. 4. This multi-stagewinding arrangement, indicated generally at 1167, includes a pluralityof winding stages a, b and c, each having a plurality of coils 1177-1 to1177-8, 1179-1 to 1179-8 and 1181-1 to 1181-8. Each of the coils has atleast one conductor turn with opposite side portions 1185 received orotherwise accommodated in respective ones of slots 1165. Most, or atleast some, of coils 1177, 1179, 1181 in winding stages a, b, c have aside turn portion 1185 thereof sharing a respective one of slots 1165with a side turn portion of other coils in the same winding stage,respectively. Two pairs of coils 1179 in winding stage b have a sideturn portion 1185 thereof sharing respective ones of slots 1165 with twopairs of coils 1177, 1181 in winding stages a and c. Two pairs of coils1177, 1179 of winding stages a and b have a side turn portion thereofwhich do not share a respective one of slots 1165.

FIG. 5 shows an alternative stationary assembly of an ECM that may beused in the present invention in lieu of the motor described above. Anexample of such alternative ECM is disclosed in the abovementionedpatent application Ser. No. 802,484, now U.S. Pat. No. 4,169,990incorporated by reference herein. In this alternative example, thewinding configuration comprises a 24 slot stator of a three-stage, fourpole motor. Although each coil may have a plurality of conductor turns,for the sake of clarity the coils in FIG. 5 are illustrated with only asingle turn per coil in each slot.

The three winding stages in FIG. 5 are designated a, b and c, eachincluding one winding formed from four coils. For example, the windingof winding stage b has four coils. The first coil is disposed in coreslots 42 and 43, the second coil is disposed in slots 44 and 45, thethird coil is located in slots 46 and 47 and the fourth coil is in slots48 and 49. The coils may be wound consecutively, or separately and thendisposed and interconnected to produce current flow. In FIG. 5, thesymbol ○ indicates current flow away from the observer, while the dotnotation in a circle indicates current flow toward the observer.

As illustrated, the side turns of the coil create four winding sets50-53. Winding set 50 is disposed in slots 49 and 42; winding set 51 isin slots 43 and 44; winding set 52 is in slots 45 and 46; and windingset 53 is in slots 47 and 48. As illustrated, the conductor portion ofeach winding set conducts current in the same axial direction asindicated, i.e, along the axial length of the core when the winding ofwinding stage b is energized. Thus, two pairs of magnetic poles N_(b)and S_(b) are created. The winding of winding stages a and c are formedin the same manner as for winding stage b, each having four winding setswith conductor portions conducting current in the same axial directionalong the core when energized.

The three stage, four pole armature winding arrangement illustrated inFIG. 5 has a winding "spread" of 30 mechanical degrees, or 60 electricaldegrees. The "spread" is the angular expanse of adjacent core slots thatcarry the conductors of a given winding, which instantaneously conductcurrent in the same axial direction along the axial length of the core.As shown in FIG. 5, a set of windings in winding stage b occupies twoadjacent slots and all of the conductors within the set carry current inthe same axial direction along the axial length of the core. Thus, thespread is the angular expanse of the two slots occupied by the set. Inthe illustrated example, this spread is 60 electrical degrees, or 30mechanical degrees.

The torque per ampere (T/I) characteristic of such a motor is a functionof winding spread and permanent magnet arc length. It is generallypreferred to keep the T/I waveform as "flat" as possible since motorshaving steep waveforms are more subject to starting problems. Theduration of the maximum value of the T/I characteristic is increased byminimizing the winding spread and/or maximizing the length of the rotormagnet. In addition, as discussed in connection with FIGS. 3 and 4, anoptimum advance timing angle, based on rotor speed and on the L/R timeconstant of the windings, is selected to advance the commutation of thewindings and permit a reduction in the arc length of the magnet. Thefunctional relationship of these factors on a per pole basis isexpressed by the following relationship: ##EQU5## An appropriate angleof advance timing is 5°-30°. The expression for spread assumes tht acore having uniform slot punchings is utilized and that all of the slotshave winding turns in them. In addition, the expression for spreadassumes a measurement from center line to center line of the teethseparating the winding measured from adjacent windings. The expressionignores second and third order tooth effects due to tooth width andtooth tip saturation, respectively.

Referring again to FIG. 5, the winding spread for winding of the 3-stagephase, 4-pole motor is 60 electrical degrees or 180°/N. The "on" timefor each winding is 180 (N-1)/N, or 120 electrical degrees. Thus, theoptimum permanent magnet arc length for a motor employing the stationaryarmature illustrated in FIG. 5 is 180 electrical degrees minus 10°-60°,depending on the optimum timing angle determined as a function of theload and speed of the motor.

FIG. 6 illustrates an ECM-driven laundry machine 8 in one form of thepresent invention. The machine may be powered by a motor of the typedescribed above in connection with FIGS. 3-5, through a transmissionsuch as shown in FIGS. 20A-20D. Accordingly, in the discussion belowreference is made to the apparatus shown in FIGS. 3, 6 and 20.

The cabinet of laundry machine 8 has a base 1357 with a plurality ofadjustable or leveling support feet 1359 thereon. An outer or uppercabinet structure 1351 has the lower end portion thereof supported on,or otherwise connected to, base 1357 by suitable means, and the upperend portion of the upper cabinet structure supports or is otherwiseconnected with a cover 1363 therefor. Sealing means, such as a resilientgasket 1365 or the like for instance, is sealably fitted or otherwiseinterposed between the upper end portion of the cabinet structure 1351and cover 1363.

Laundry machine 8 is provided with a supporting frame 1367 on whichtransmission mechanism 1245, electronically commutated motor 30, a pumpdevice 1369 for the laundry machine, spin tub 10 and agitator 12 aresupported generally in vertically aligned or in-line relation, asdiscussed hereinafter. Frame 1367 is suspended or otherwise mountedwithin cabinet 1351 on a plurality of brackets 1371 suitably attached tobase 1357 by a plurality of damping means 1373; however, for the sake ofsimplicity only one of such bracket and damping means is shown in FIG.6. Each vibration damping means 1373 has resilient means, such as a coilspring 1375 or the like for instance, biased or otherwise interconnectedbetween bracket 1371 and frame 1367. Other resilient means, such as agenerally U-shaped spring clamp 1377 or the like, is secured to thebracket having a pair of depending prestressed legs 1379 straddling apart 1381 of the frame in gripping engagement therewith with resilientfriction pads 1383 interposed between the legs and the frame part,respectively. Thus, vibration damping means 1373 acts not only to limitor damp twisting or torquing movement but also vertical movement offrame 1367 which may be imparted thereto particularly during the wash orspin cycles of the laundry machine.

A platform or other upstanding structure 1385 is generally centrallyprovided on frame 1367 and integrally connected thereto by suitablemeans (not shown). Lower end wall 1251 on casing 1249 of transmissionmechanism 1245 is seated on an upper free end or seat 1387 of theplatform being connected thereto by suitable means, such as a pluralityof nuts and bolts 1389 or the like, arranged with mounting openings 1275in the lower end wall and aligned mounting openings 1391 in theplatform. ECM 30 is seen to be mounted to transmission mechanism 1245 soas to depend therefrom toward frame 1367. Shaft extension 1157 onrotatable assembly shaft 1151 of the ECM is journaled in bearing means1281 disposed in lower end wall 1251 of transmission mechanism casing1249 so as to constitute input shaft 1287 of the transmission mechanism.Input gear 1291 is mounted on the free end of shaft extension 1157 so asto be conjointly rotatable with rotatable assembly 1151 of the motorupon the energization thereof. The other end shield 1217 ofelectronically commutated motor 30 may also be removed so that flange1225 of housing sleeve 1219 is abutted against pump 1369, and the othershaft extension 1159 of rotatable assembly 1151 extends into drivingengagement with the pump of laundry machine 8. Pump 1369 is secured toflange 1225 of motor 30 by suitable means, such as a plurality of nutsthreadedly received on a stud plurality extending from the pump. Whilethe aforementioned mounting arrangements or interconnections oftransmission mechanism 1245 to platform 1385, electronically commutatedmotor 30 to the transmission mechanism, and pump 1369 to the motor havebeen illustrated herein for the purposes of disclosure, it iscontemplated that various other mounting arrangements orinterconnections may be made between such components of laundry machine8 within the scope of the present invention so as to meet at least someof the objects thereof.

In FIG. 6, tub 10 is seen to include a generally annular perforatesidewall 1399 having a base wall 1401 integrally interconnectedtherewith. A generally central opening 1403 extends through the basewall. Means, such as a collar 1405 or the like, is provided for securingtub 10 to tubular output shaft 1293 of transmission mechanism 1245. Thesecuring means of collar extends through opening 1403 in tub base wall1401, being grippingly and sealably engaged with the opposite sidesthereof generally about the opening. Although not shown, the tubularoutput shaft 1293 extending exteriorly of transmission mechanism casing1249 is connected by suitable means with collar 1405 so that tub 10 isconjointly unidirectionally rotatable with the tubular output shaftduring the spin cycle of laundry machine 8, as discussed hereinbelow.Further, upper end 1305 of output shaft 1303, which extends exteriorlyof transmission mechanism casting 1249 and coaxially through tubularoutput shaft 1293, is connected by suitable means (not shown) withagitator 12 so that the agitator is conjointly oscillated with outputshaft 1303 during the wash cycle of laundry machine 8.

An intermediate or enclosing tub 1407 is provided with a sidewall 1409spaced generally between spin tub sidewall 1399 and the upper cabinetstructure. A base wall 1411 is integrally formed with the enclosing tubsidewall, having a generally centrally located opening therethroughdefined by an integral generally annular flange depending from the basewall in spaced relation generally adjacent casing 1249 of transmissionmechanism 1245. A hose 1419 or other flexible connection for instance isconnected between base wall 1411 of enclosing tub 1407 and pump 1369providing a passage for the removal from the enclosing tub of waterselectively discharged into tub 10 through a nozzle 1421.

Before proceeding with the discussion of the operation of laundrymachine 8, it is appropriate to discuss in greater detail the exemplarytransmission shown in FIGS. 20A-20D. Casing or cover 1249 oftransmission mechanism 1245 encases a bearing support or housingindicated generally at 1263, disposed within a chamber 1265 of thecasing. Bearing support 1263 includes a pair of cylindrical sidewalls1267, 1269 with sidewall 1267 being seated on casing end wall 1251. Anintermediate support wall or plate 1271 is interconnected betweensidewalls 1267, 1269. An upper support wall or plate 1273 is connectedto the upper end of sidewall 1269 generally adjacent end wall 1253 ofcasing 1249. A plurality of mounting openings 1275 may be provided incasing 1249 so as to mount transmission mechanism 1245 in laundrymachine 8 as discussed above. Opposite end walls 1251, 1253 have a pairof openings 1277, 1279 extending therethrough so as to intersect withchamber 1265. A pair of bearing means 1281, 1283 is supported in theopenings in journaling engagement with input means 1255 and output means1257, respectively. If desired, a plurality of mounting studs 1285 maybe integrally or otherwise provided on lower end wall 1251 so as toextend thereform for receiving electronically commutated motor 30 whentransmission mechanism 1245 is mounted in laundry machine 8, asdiscussed above.

Input means 1255 includes an input shaft 1287 journaled in bearing means1281 and extending through opening 1277 in end wall 1251, with a freeend or end portion 1289 disposed generally adjacent end wall 1251 withinchamber 1265. An input or pinion gear 1291 within chamber 1265 iscarried on free end 1289 of input shaft 1287 so as to be conjointlyrotatable therewith. The input shaft is adapted to be rotated or drivenunidirectionally or, alternatively, to oscillate in opposite directions.

Output means 1257 includes a tubular output shaft 1293 having agenerally axial bore 1295 therethrough. The tubular output shaft extendsthrough opening 1279 in casing end wall 1253. Output shaft 1293 isjournaled in bearing means 1283 in casing end wall 1253 and extendsthrough support wall 1273. Thus, a lower interior or free end of theoutput shaft is journaled in another bearing means 1297 disposed inanother opening extending through intermediate support 1271. An output,driven or pinion gear 1301 is carried about tubular shaft 1293 so as tobe conjointly rotatable therewith. The output gear is arranged so as toextend from the tubular shaft generally in spaced relation betweensupports 1271, 1273.

Output means 1259 includes an output shaft 1303 which extends generallycoaxially through bore 1295 of tubular shaft 1293. Output shaft 1303 hasan exterior or free end or end portion 1305 exteriorly of chamber 1265,with an opposite interior free end or end portion 1307 disposed withinthe chamber. Although not shown, interior end 1307 of output shaft 1303is journaled in a bearing means provided therefor in casing end wall1251. Exterior end 1305 of output shaft 1307 may be journaled insuitable bearing means (not shown) provided therefor. Another output,driven or pinion gear 1309 is carried by output shaft 1303, generallyadjacent interior end 1307 thereof, so as to be spaced between casingend wall 1251 and support wall 1271 within chamber 1265.

Transmitting means 1261 is provided for transmitting the rotationalmovement of input shaft and gear 1287, 1291 to tubular output shaft andgear 1293, 1301 and to output shaft and gear 1303, 1309, respectively.Transmitting means 1261 includes means, such as a driving or idler shaft1311 and a pinion gear 1313 carried thereon, associated in coupledrelation with output shaft and gear 1303, 1309 for driving it, andmeans, such as a driven or idler shaft 1315 and a pinion gear 1317carried thereon, associated in coupled relation with input shaft andgear 1287, 1291 for being driven by it. Driving and driven means oridler shafts 1311, 1315 each have a pair of opposite end portions 1319,1321 and 1323, 1325 journaled in a pair of bearing means 1327, 1329 and1331, 1333. Bearing means 1327, 1331 are disposed in casing end wall1251 and bearing means 1329, 1333 are disposed in upper support wall1273, respectively. Driven idler shaft 1315 has a plurality of splines1335 extending axially thereabout between its opposite ends 1323, 1325.Pinion gear 1317 is carried on the driven idler shaft generally adjacentlower opposite end 1323 thereof in meshing engagement with input gear1291. Thus, the mesh between input gear 1291 and pinion gear 1317effects the concert driven rotation of idler shaft 1315 with input shaft1287. Pinion gear 1313 is carried on driving idler shaft 1311 so as tobe arranged in meshing engagement with output gear 1309 on output shaft1303. Thus, the meshing engagement between pinion gear 1313 and outputgear 1309 effects the conjoint driven rotation of output shaft 1303 withthe driving idler shaft. Another pinion gear 1337 is also carried onidler shaft 1311 generally in spaced relation with pinion gear 1313thereon.

Transmitting means 1261 also includes means, such as a pair ofinterconnected stepped shifting gears 1339, 1341, selectively movablebetween a plurality of shifted positions with respect to idler shafts1311, 1315 and operable generally in one of the shifted positions (asbest seen in FIG. 20A) for coupling idler shaft 1315 with tubular outputshaft 1293 and in another of the shifted positions thereof (as best seenin FIG. 20C) for coupling idler shaft 1315 with idler shaft 1311. Asplined bore 1343 is coaxially provided through coupling means orstepped shifting gears 1339, 1341. Splines 1335 on idler shaft 1315 arecooperatively received in the splined bore so that the stepped shiftinggears are axially movable between at least the upper shifted or spinposition and the lower shifted or agitating position thereof on idlershaft 1315. Stepped shifting gears 1339, 1341 may also be provided witha third shifted position, such as a neutral or pump operating position,disengaged from output shafts 1293, 1303. Thus, through the engagementof splines 1335 on idler shaft 1315 with splined bore 1343 of steppedshifting gears 1339, 1341, the stepped shifting gears are not onlyaxially movable or shiftable on idler shaft 1315, but also conjointlyrotatable therewith in response to the rotation of input shaft 1287.Larger stepped shifting gear 1341 is arranged in meshing engagement withoutput gear 1301 on tubular output shaft 1293 when stepped shiftinggears 1339, 1341 are in the upper shifted position thereof. Smallershifting gear 1339 is arranged in meshing engagement with intermediatepinion gear 1337 on idler shaft 1311 when the stepped shifting gears arein the lower shifted position thereof.

A shift actuating device, schematically shown and indicated generally at1345, is selectively operable for moving a linkage 1347 thereof toeffect the shifting axial movement of stepped shifting gears 1339, 1341connected with the linkage between the shifted positions of the steppedshifting gears on idler shaft 1315. However, while the shift actuatingdevice and linkage are illustrated herein in association with steppedshifting gears 1339, 1341, for purposes of disclosure it iscontemplated, within the scope of the present invention, that othermeans may be employed for effecting the shifting of the stepped shiftinggears between the shifted positions thereof, i.e., shifting transmissionmechanism 1245 between its aforementioned operating modes.

With respect to the operation of transmission device 1245, it will berecalled that input shafft 1287 may be driven or operated so as to beoscillatable in one operating mode of the transmission mechanism andunidirectionally rotated in another operating mode of the transmissionmechanism. When input shaft 1287 is unidirectionally rotated, linkage1347 is actuated by shifting device 1345 so that stepped shifting gears1339, 1341 are in the upper shifted position thereof (as best seen inFIG. 20A) wherein larger stepped shifting gear 1341 is meshed withoutput gear 1301 of tubular output shaft 1293. In this manner,unidirectional rotation of input shaft 1287 is transmitted throughmeshed input gear 1291 and pinion gear 1317 to idler shaft 1315, toeffect the conjoint unidirectional rotation thereof with the inputshaft. Since splines 1335 on idler shaft 1315 are received in splinedbore 1383 of stepped shifting gears 1339, 1341, the stepped shiftinggears are conjointly unidirectionally rotated with idler shaft 1315.This conjoint unidirectional rotation of the shifting gears istransmitted through meshed larger stepped shifting gear 1341 to outputgear 1301 on tubular output shaft 1293 so as to effect the conjointunidirectional rotation thereof with the stepped shifting gears. Thus,in the one operating mode of transmission mechanism 1245, as determinedby shifting device 1287 is transmitted to tubular output shaft 1293effecting the conjoint unidirectional rotation thereof with the inputshaft while output shaft 1303 remains at rest.

When linkage 1347 is actuated by shifting device 1345 so as to axiallymove stepped shifting gears 1339, 1341 downwardly toward its lowershifted position on idler shaft 1315 (as best seen in FIG. 20C) largerstepped shifting gear 1341 is disengaged from output gear 1301 ontubular output shaft 1293, and smaller stepped shifting gear 1339 ismoved into meshing engagement with intermediate pinion gear 1337 onidler shaft 1311. With stepped shifting gears 1339, 1341 in their lowershifted position, transmission mechanism 1245 may function in its otheroperating mode, with input shaft 1287 being oscillatably rotatable.Thus, the oscillation of input shaft 1287 is transmitted through meshedinput gear 1291 and pinion gear 1317 to idler shaft 1335 to effect theconjoint oscillation thereof with the input shaft. Since splined bore1343 of stepped shifting gears 1339, 1341, is received on splines 1335of idler shaft 1315, the stepped shifting gears are conjointlyoscillated with idler shaft 1315. Such conjoint oscillation istransmitted to idler shaft 1311 through the meshing engagement ofsmaller stepped shifting gear 1339 with intermediate gear 1337 on idlershaft 1311. This conjoint oscillation of idler shaft 1311 with idlershaft 1315 is transmitted to output shaft 1303 through the meshingengagement of pinion gear 1313 on idler shaft 1311 with output gear 1309on output shaft 1303. Thus, the oscillation of input shaft 1287 istransmitted to output shaft 1303 during the other operating mode oftransmission mechanism 1345.

Reverting now to the operation of laundry machine 8, let it be assumedthat stepped shifting gears 1339, 1341 in transmission mechanism 1245are disposed in the lower shifted or agitation position thereof, withsmaller stepped shifting gear 1339 driving output shaft 1303 through themeshing engagement of the smaller shifting gear, with intermediate gear1337 on idler shaft 1311 and the meshing engagement of pinion gear 1313thereon with output gear 1309 on the output shaft, as further discussedhereinbelow with respect to FIGS. 20A-20D. With transmission mechanism1245 so set or shifted to effect the wash cycle of laundry machine 8,water may be introduced through nozzle 1421 into spin tub 10 so that itflows through the perforations therein into enclosing tub 1407. Clothesto be laundered in the water and a charge of detergent or the like (notshown) may also be placed in the spin tub. Of course, the level to whichthe water rises in enclosing tub 1407 may be controlled by any suitablefluid level sensing means, as well known in the art. With thispreparation, electronically commutated motor 30 may be energized tocommence the wash cycle of the laundry machine. Upon the energization ofthe motor, winding stages a, b and c are commutated so as to bealternately excited in the aforementioned preselected differentsequences. This effects the magnetic coupling therewith of rotatableassembly 1151 so as to impart oscillating movement or rotation to thelatter. This oscillating motion may be of any desired or preselectedfrequency, as explained in greater detail hereinbelow. It may also be ofany desired or preselected amplitude, depending on the selected controlfunctions, as explained elsewhere in this specification.

The oscillating motion of rotatable assembly 1151 is translated ortransmitted by transmission mechanism 1245 to its output shaft 1303which is drivingly connected or otherwise associated with agitator 12 soas to effect the conjoint oscillation thereof with the rotatableassembly of electronically commutated motor 30. In this manner, theoscillator motion of the agitator within tub 1353 effects the agitationand laundering of the clothes therein. Although not shown in thedrawings, pump 1369 may include means for pumping water from enclosingtub 1407 through a filter back into spin tub 10 in order to trap orfilter out much of the lint which may be separated from the clothes asthey are laundered during the above-discussed wash cycle of the launderymachine. After laundry machine 8 has been operated for a desired orpreselected period of time in its wash cycle, electronically commutatedmotor 30 may be deenergized or braked to terminate the cycle.

Subsequent to the wash cycle of laundry machine 8 and in order toinitiate the spin cycle thereof, shifting device 1345 for transmissionmechanism 1245 may be actuated. This will cause its linkage 1347 to movestepped shifting gears 1339, 1341 upwardly on idler shaft 1315 towardthe spin or upper shifted position thereof, as shown in FIG. 20A, sothat larger stepped shifting gear 1341 is meshed with output gear 1301on tubular output shaft 1293. At this time, motor 30 may be reenergizedwith its winding stages a, b and c commutated so as to be excited in apreselected sequence. Magnetic coupling with rotatable assembly 1151 iseffected in the manner discussed hereinabove to impart unidirectionalrotation thereto. As discussed below, the unidirectional speed ofrotatable assembly 1151 may be of any desired or preselected magnitude.It is contemplated that the speed of the unidirectional rotation of therotatable assembly will be appreciably greater than the speed of theabove discussed oscillation motion.

With stepped shifting gears 1339, 1341 moved into the upper shiftedposition in transmission mechanism 1245, the unidirectional rotation ofrotatable assembly 1151 is translated or transmitted by the transmissionmechanism to its tubular output shaft 1293 which is drivingly connectedor otherwise associated with tub 10 so as to effect the conjointunidirectional rotation thereof with the rotatable assembly ofelectronically commutated motor 30. In this manner, the unidirectionalrotation of spin tub 10 is operative to effect the centrifugaldisplacement of water from the clothes within the spin tub. Pump 1369may, if desired, be arranged to be driven by motor 30, as discussedhereinbelow, and includes means for effecting the removal of water fromspin tub 10 and enclosing tub 1407, through hose 1419 to a drain (notshown). After laundry machine 8 has been operated for a desired orpreselected period of time in its spin cycle, electronically commutatedmotor 30 may be de-energized or braked so as to terminate the spincycle.

To complete the operation of laundry machine 8, shifting device 1345 maybe selectively actuated to operate linkage 1347 and move steppedshifting gears 1339, 1341 to their neutral position as previouslymentioned, in order to bring about a pumping cycle of the laundrymachine during which water is expelled. In their neutral position,stepped shifting gears 1339, 1341 are disengaged from output gear 1301on tubular output shaft 1293 and from intermediate gear 1337 on idlershaft 1311. The latter is drivingly connected, through its gear 1313,with output gear 1309 on output shaft 1303. Therefore, with steppedshifting gears 1339, 1341 in their neutral position, electronicallycommutated motor 30 may be energized to drive pump 1369, while being ineffect drivingly disconnected from spin tub 10 and agitator 12 bytransmission mechanism 1245.

It will be understood that the discussion above of laundry machine 8does not dwell on all of the valving and particular controls normallyprovided on modern domestic laundry machines. The omission of thesecomponents is primarily for the purpose of brevity; however, it iscontemplated that such components may be provided in the laundry machineand that such laundry machine may be provided with other operating modesor cycles within the scope of the invention.

It will be clear from the discussion above that tub 10 and agitator 12of laundry machine 8 are arranged to follow the basic motion of thedriving ECM. Accordingly the combination of the laundry machine and ofthe ECM, as shown in FIG. 6, dispenses with the need for a clutch, abelt transmission and a compensating balancing weight used by prior artlaundry machines of the kind illustrated in FIG. 1. While the inventionis not limited to the transmission shown in FIGS. 20A-20D, it is clearthat the mechanism between the laundry machine and the ECM must becapable of selectively applying the motion of the ECM rotor shaft to thetub and agitator respectively of the laundry machine. Although thelatter components can be driven at the ECM rotor angular velocity, astep-down gear ratio is advantageously employed, at least for portionsof the operation, in order to minimize motor size. In Table A below,exemplary combinations of RPM, gear ratio and voltage are listed whichmay be employed for a direct drive washing machine of the type shown inFIG. 6.

                  TABLE A                                                         ______________________________________                                        MOTOR     GEAR RATIO     MOTOR VOLTS                                          RPM       WASH    SPIN       WASH   SPIN                                      ______________________________________                                        140       1:1     1:1        32     80                                        700       5:1     1:1        80     80                                        700       5:1     5:1        32     80                                        1400      10:1    2:1        80     80                                        1400      10:1    10:1       32     80                                        ______________________________________                                    

In the foregoing table the motor RPM column is referenced to the peakspeed of the wash cycle. For example, for a fixed 1:1 gear ratio, i.e.using no step down ratio, the motor would be operated at a peak voltageof 32 volts for the wash cycle and at 80 volts for the spin cycle. Whilethe 80 volt value is an arbitrary selection, the 32 volt value isrelated to the spin-to-wash ratio of angular velocity. Alternatively, a5:1 gear ratio may be interposed for the wash cycle, while resetting toa 1:1 ratio for spin. The voltages involved in the latter case are 80volt peak for both wash and spin cycles. Other gear ratio possibilitiesare identified in Table A above, together with their associated voltageand RPM values.

As previously stated, the purpose of introducing gear ratios between theshaft of the ECM rotor and the drive shaft of the laundry machine is toreduce the size of the ECM. While a 1:1 gear ratio for both the wash andspin cycles is possible, it requires a larger motor and may, for thatreason, be the costlier alternative. On the other hand, if a 5:1 gearratio is used for the wash cycle alone, a motor of smaller size may beused.

Another criterion to keep in mind is that the inertia of the rotor mustremain small compared to the inertia reflected from the agitator.

                  TABLE B                                                         ______________________________________                                        GEAR RATIO 1:1        5:1         10:1                                        ______________________________________                                        Peak θ Degrees                                                                      160        800 (2.2 REV)                                                                             1600                                                                          (4.4 REV)                                  Peak ω Rad/Sec                                                                      14.65      73.25       146.5                                      (RPM)       (140)      (700)       (1400)                                     Peak α Rad/Sec.sup.2                                                                153.5      767.5       1535                                       Moment of inertia                                                                         .168       .00672      .00168                                     (Agitator)                                                                    oz ft Sec.sup.2                                                               Friction Constant                                                                         12.83      .513        .128                                       (Agitator)                                                                    oz ft Sec/Rad                                                                 Moment of Inertia                                                                         .027       .0046       .0023                                      (Motor)                                                                       oz ft Sec.sup.2                                                               Peak Friction                                                                             188        38          19                                         Torque oz ft                                                                  Peak Inertia                                                                              30         8.7         6                                          Torque oz ft                                                                            ↑  ↑                                                              MOTOR &  REFERRED TO MOTOR                                                    AGITATOR                                                            ______________________________________                                    

Table B above shows that the latter would be the case, up to a 5:1 gearratio, where the agitator undergoes essentially sinusoidal motion.Moment of inertia and friction constant are both reflected to the motorby a factor of the gear ratio squared. Energy to be dissipated by thesystem as the torque passes through zero at the point of reversal of theagitate cycle is Iω² /2. The inertia should be kept as small aspossible, since the moment of inertia, I, affects the energy to bedissipated upon reversal, as well as the angular velocity ω at thetorque zero crossing. The larger the value of I, the greater the lagangle β between torque and angular velocity and the larger the value ofω at the zero crossing. The friction load also affects the value of ω.As it drops off, β increases and ω at the torque zero crossingincreases. This accounts for the importance of maintaining the rotorinertia small. Tabe B above summarizes the physical constants involvedrelative to the wash cycle, for exemplary gear ratios of 1:1, 5:1 and10:1. The moments of inertia shown in Table B are based on motorspecimen which may be advantageously employed in the present invention.

                  TABLE C                                                         ______________________________________                                        GEAR RATIO    1:1         5:1     10:1                                        ______________________________________                                        Largest ω RPM                                                                         600         3000    6000                                        Largest α Rad/Sec.sup.2                                                               1.57        7.85    15.7                                        Largest Moment of                                                                           15.5         .62     .16                                        Inertia oz ft Sec.sup.2                                                       Largest Friction                                                                            66          13.2     6.6                                        Torque oz ft                                                                  Largest Inertia                                                                             24           4.9     2.4                                        Torque oz ft                                                                              ↑   ↑                                                             MOTOR     REFERRED                                                            & TUB     TO MOTOR                                                ______________________________________                                    

Table C lists the physical constants for the spin cycle of the laundrymachine for the three gear ratios discussed above. For each ratiosetting a separate peak torque exists, e.g. 66 oz ft for a 1:1 ratio. Incontrast to the use of a slip clutch in prior art laundry machines forlimiting the maximum torque applied, the present invention permitstorque control by limiting the current to the motor windings, as will bediscussed in greater detail below.

FIG. 7 illustrates the angular velocity/torque characteristics fordifferent applied voltages, as well as the performance of an ECM using a5:1 gear ratio for the wash cycle and a 1:1 gear ratio for the spincycle. As shown by the set of straight lines, motor speed decreaseslinearly as the load on the motor increases. The area enclosed by linesdesignated by the letter S applies to the spin cycle and that designatedby the letter W applies to the wash cycle. Within the operatingparameters of the wash cycle, the two broken line curves represent theangular velocity/torque performance for full load and half loadrespectively, during the positive stroke of the back-and-forthsinusoidal motion of the agitator. The performance curves for thenegative stroke are substantially the same, except for direction,provided the two strokes are otherwise identical. Since the sameconsiderations apply, the illustration of the negative stroke has beenomitted in order to simplify the explanation herein.

It will be noted that the angular velocity/torque performance curves forthe wash cycle have an elliptical shape, bearing in mind that only onehalf of each curve is shown in FIG. 7. The elliptical shape is caused bythe inertia of the system which results in a net loss of energy when themotion of the agitator is reversed. For an applied voltage of 80 V,maximum torque is developed slightly after the maximum angular velocityof 700 RPM is reached, consonant with the characteristics illustrated inFIG. 2E. Thereafter, angular velocity and torque diminish in preparationfor motion in the reverse direction.

When the agitator reaches zero torque, it is seen to have an angularvelocity of approximately 270 RPM at half load and approximately 140 RPMat full load. A negative torque is required to bring the rotationalassembly to zero angular velocity. This work represents energy whichmust be dissipated, and which may have a peak value of approximately 245watts at full load for the example selected. A number of techniques maybe used for implementing such dissipation of energy, all of them readilycarried out where an electronically commutated motor drives the laundrymachine. They are as follows:

1. Coasting and letting the load in the laundry machine absorb theenergy.

2. Shorting the stator winding stages.

3. Feeding the energy back to its source capacitor.

4. Using a controlled plug reverse, i.e. reversing the terminals of thestator winding stages.

In FIG. 7, the lines designated by the letter S represent an idealizedangular velocity/torque performance curve for the spin cycle. As shown,the angular velocity remains substantially at the zero level until thedesired torque is built up, i.e. the tub will not begin to turn until atorque of approximately 66 oz ft is applied in the example underconsideration. By limiting the current applied to the windings of theECM, the torque is maintained at that level while the angular velocityof the rotatable assembly builds up to its full 600 RPM value. It willbe understood that in practice there is some increase of the rotorangular velocity as the pre-set torque level is gradually attained.Likewise, at some point in mid-velocity range, e.g. at approximately 300RPM, the load will drop below the maximum torque of 66 oz ft and willfollow a diagonal rather than a vertical path to full speed.

In a preferred embodiment of the invention, explained in greater detailbelow, a combination of the first three energy dissipation techniqueslisted above is used, combined with a dynamic braking feature whichadapts to existing operating conditions. The motor windings are eithershorted outright or across a resistor. Thus, while some coasting ispermitted, the motor is brought to a halt quickly. The resultant effecton the load in the laundry machine is not as harsh and destructive as isthe case where a plug reversal is used.

FIG. 8 illustrates the angular velocity/torque characteristics andperformance of the ECM discussed above, using a 1:1 gear ratio for boththe wash and the spin cycle. To conserve space, the torque coordinate isdrawn to a different scale than that in FIG. 7. As shown, torque demandis up by a factor of 5 in the wash cycle, as compared to the situationillustrated in FIG. 7. Although the elliptical shape of the speed/torquecharacteristic during the wash cycle is retained, the energy which mustbe dissipated as the torque changes from positive to negative isapproximately 30% less than is the case for the situation shown in FIG.7.

Assuming the maximum torque of the motor in FIG. 7 is 66 oz ft, arelatively small motor suffices for the 5:1/1:1 gearing arrangement,which is used nearly to capacity in the wash and spin cycles. However,in addition to the 30% saving in energy which needs to be dissipated,the arrangement of FIG. 8 also eliminates the need for transmissiongearing for ratio step down purposes. Clearly then, the selection of thegear ratio employed depends in large measure on the particularobjectives set for the machine.

FIGS. 9-11 show various performance characteristics of one embodiment ofan ECM coupled to a laundry machine, in one form of the invention usinga 5:1 gear ratio for the wash cycle and a 1:1 gear ratio for the spincycle. These characteristics apply to a 24 slot, 4 pole motor, utilizingcopper wire and cobalt-samarium magnets and having a rotor moment ofinertia of 0.0046 oz ft sec². The angular velocity/torque characteristicω/T shown in FIG. 9 is identical to that shown in FIG. 7 for an appliedvoltage of 80 V and is the same for the wash and spin cycles. Thecurrent/torque characteristic, I/T, is linear. Its intersection with ω/Tdetermines that the current required to develop the maximum requiredtorque of 66 oz ft at a rotor speed of 600 RPM is about 6 amps.

FIG. 10 illustrates the relationship of motor efficiency to the angularvelocity of the rotatable assembly, as it applies to the wash cycle. Asshown, in the vicinity of 600 and 700 RPM, (see FIG. 9), motorefficiency is highest, i.e. on the order of 75% for increasing rotorvelocity and slightly higher for decreasing rotor velocity. For the fullwash cycle the efficiency is estimated to be between 65%-70%. Theefficiency curve shown in FIG. 10 takes into account motor losses aswell as associated solid state losses.

FIG. 11 illustrates the efficiency/torque characteristic for the spincycle, for a median angular velocity of 700 RPM's and an applied voltageof 80 volts. The solid line curve in FIG. 11 shows efficiency when motorlosses alone are taken into consideration, while the dashed line curvealso takes into account solid state losses. At maximum torque, theefficiency is estimated to be somewhat greater than 60%.

FIGS. 12-14 show the characteristics of a 24-slot, 4-pole motor having amoment of inertia of the rotatable assembly of 0.27 oz ft sec² and usingmaterials similar to those used for the motor discussed above inconnection with FIGS. 9-11. A 1:1 gear ratio applies for both the washand the spin cycle and hence a larger motor is required due to highertorque demand. The angular velocity/torque characteristics, ω/T, areseen to be different in FIG. 12 for the wash and the spin cyclesrespectively. Likewise, the I/T characteristics show that currents ofdifferent amplitude are required to develop the same torque. In theexample under consideration, the voltage applied for the spin cycle wasa full 80 volts, while a reduced value of 32.5 volts peak was appliedfor the wash cycle.

FIG. 13 shows the efficiency curve for the wash cycle plotted againstangular velocity. Here again, the efficiency at decreasing rotorvelocity is slightly higher than at increasing speed, neither however,rising above an efficiency at 45%.

FIG. 14 illustrates efficiency plotted against the torque developed bythe motor. As before, the solid line curve takes into considerationmotor losses alone, while the dashed line curve includes motor losses aswell as associated solid state losses. At a torque of 66 oz ft, theefficiency is seen to approach 90%. This is also the efficiency for theoverall spin cycle.

FIG. 15 illustrates in schematic form a laundering system in accordancewith the principles of the present invention. Laundry machine 8 includesbasket or tub 10 and coaxially mounted agitator 12, both adapted torotate independently or jointly about their common axis. Anelectronically commutated motor 30 is adapted to be coupled to the driveshaft of machine 8 through a connection mechanism which may take theform of transmission 1245 discussed above in connection with FIGS.20A-20D. Further, the transmission may include gearing to establishdesired angular velocity and torque ratios, as explained above. Powerderived from a 115 V, 60 Hz AC line is rectified 70 and applied to apower conditioning circuit 72. The latter operates on the rectifiedsignal in accordance with external conditions and parameters, asdetermined by an applied command signal. The latter acts to control theapplication of the rectified signal with respect to amplitude, durationand timing. The output of power conditioning circuit 72 takes the formof an effective DC voltage V_(M) which is applied to power switchingmeans or circuit 74. The operation of the latter is controlled from acommutation circuit 76 which acts to apply the effective voltage to thewinding stages of ECM 30 in a selected sequence. The motion of therotatable components 10 and 12 of laundry machine 8 is thus controlledby the applied command, as well as by the action of the commutationcircuit.

FIG. 16A shows the essential components of a control system foroperating the apparatus of FIG. 15 in accordance with the principles ofthe present invention. As before, applicable reference numerals havebeen carried forward from earlier Figures. Rectifier circuit 70 is seento consist of a full wave diode bridge having a pair of nodes connectedacross a 115 V, 60 Hz power line. The other pair of nodes of rectifierbridge 70 is connected to line 82 and common line 80. The DC voltagewhich appears across these lines takes the form of a full wave rectifiedsignal, as shown by waveshape 100 in FIG. 16B. A silicon controlledrectifier 90 is connected in series between lines 82 and 82' and acts asa switch in the line to connect or interrupt power to the remainder ofthe control circuit. A capacitor 78, which may have a capacity on theorder of 2500 uf, is connected across line 82' and 80 and serves as aripple filter to smooth out the rectified waveform appearing acrossthese lines. A current shunt 96 is connected in series between lines 80and 80'.

The motor is preferably of the type discussed above in connection withFIGS. 3-5, i.e. an electronically commutated motor having three windingstages, although other types of ECM's may be used. The stator windingstages a, b and c respectively, are shown to be connected in a singleended configuration, i.e. with one winding terminal connected to line82'. The other terminals of winding stages a, b and c are connected tothe collectors of a set of commutation transistors 84, 86 and 88respectively, whose emitters are jointly connected to line 80'.Transistors 84, 86 and 88 thus collectively form the power switchingcircuit 74 of FIG. 15, the transistor bases being connected to receivesignals from commutation circuit 76 in accordance with applied positionsignals. The latter signals may be provided by a position sensor 120,shown in FIG. 24. As explained in the aforesaid copending applicationSer. No. 802,484, now U.S. Pat. No. 4,169,990, optical, magnetic, orother physical effects may be employed to provide the aforesaid signals.In the present invention, the position sensing circuit is preferablyactuated by back EMF signals derived from the aforesaidcollector-connected terminals of winding stages a, b and c. Thesesignals, which are proportional to rotor angular velocity, aresubsequently integrated to provide the desired position signals.

SCR 90, which is normally cut off, is controlled from a regulator 92which is responsive to a number of different input signals. Although SCR90 is conceptually part of the regulation circuit, it is shownseparately herein to facilitate an understanding of the invention. Itwill be understood that SCR 90, regulator 92 and capacitor 78 all formpart of the power conditioning circuit which is indicated by block 72 inFIG. 15.

A first input signal of regulator 92, applied at terminal 93, is derivedfrom an external source and is representative of the desired motorperformance. In a laundry machine environment in accordance with thepresent invention, this signal may be provided by a microcomputer inresponse to instructions dialed or otherwise set into the laundrymachine control panel. It will be understood, however, that theinvention is not so limited and that signals representative of motorperformance may be generated in different ways. A second regulator inputsignal is derived from a zero crossing detector unit 94, which isconnected across the output of diode bridge 70. A pair of lines 146,148, connected across current shunt 96, provide a further input toregulator 92. Line 146 serves as a common voltage reference at theregulator input. The signal derived across the current shunt isproportional to the current in the winding stages and it is furtherconnected to the input of commutation circuit 76.

As previously explained, capacitor 78 serves to smooth out the ripple inthe signal which appears between lines 82' and 80. Thus the effectivevoltage V_(M) applied to winding stages a, b and c is a substantiallyripple-free DC voltage. As shown, V_(M) is further fed back as an inputto circuit 92 for regulation purposes.

In operation, position sensing circuit 120 controls commutation circuit76. The latter, in turn, controls the timing of the energization ofwinding stages a, b and c in response to the applied rotor positionsignal, as well as controlling the sequence of winding energization.This is done by the application of signals to the bases of commutationtransistors 84, 86 and 88, which render these transistors conductive atthe desired points in time. The signal derived from current shunt 96 isproportional to motor current, which itself is representative of thetorque applied by the motor, as explained above. If the motor currentrises above a preselected value, the signal derived across resistance 96acts through commutation circuit 76 to cut off the commutationtransistors. Simultaneously, a signal is applied to regulator 92 which,by controlling V_(M), controls the amplitude of the current in thewinding stages.

In the circuit of FIG. 16A, the angular velocity of the rotatableassembly is regulated in accordance with a technique known as phaseangle control. Zero crossovers of the 60 Hz line are detected and asignal is generated at a predetermined time interval thereafter, e.g. ata phase angle of 120°. The latter signal is applied to regulator 92which responds by turning on SCR 90. Thus, the signal applied atterminal 93 which represents the desired motor performance, determinesthat power is to be supplied to the winding stages during a timeinterval corresponding to a 60° phase angle, as shown by the shaded areain FIG. 16B. In accordance with the discussion above, capacitor 78filters the signal at the output of SCR 90 to produce an effectivevoltage V_(M) which is applied to winding stages a, b and c. It will beseen therefore, that a DC voltage is applied only during a 60° intervalunder the assumed operating conditions. Thus, where phase control isemployed, the angular velocity of the rotatable assembly is controlledby preselecting the phase angle during which a DC voltage is applied tothe winding stages.

As shown in FIG. 16A, the control of the angular velocity of therotatable motor assembly may be further refined by means of voltagefeedback, whereby V_(M) is applied to regulator 92 for comparisonagainst the signal derived from terminal 93. Since V_(M) isrepresentative of the actual angular velocity of the rotatable motorassembly, such velocity will vary with the difference between thecompared signals. The resultant error signal is applied to SCR 90. Ifthe amplitude of the error signal increases, SCR 90 is conductive for alonger time interval and the motor speeds up; if it decreases, SCR 90 isopen for a shorter time interval and the drag on the rotor, e.g. due tofriction and the wash load in the laundry machine, reduces motor speeduntil the desired angular velocity is reached.

The invention is not limited to the voltage feedback technique shown anddiscussed above. For example, a further way of providing closed loopregulation of the angular velocity of the rotatable assembly, is tocompare the signal at terminal 93 with the back EMF signals applied toposition sensing circuit 120, (or with a single combined back EMFsignal), proportional to rotor velocity. In this manner the extraneousfactors introduced by the resistance and inductance of the windingstages is avoided and a more closely regulated operation of the motorresults.

As previously explained, the signal derived from current shunt 96 isapplied to commutation circuit 76 and thence to the base of eachcommutation transistor, as well as to regulator 92. While the regulationof V_(M) is carried out by unit 92 in the circuit illustrated in FIG.16A, such action may not respond sufficiently quickly to an over-currentcondition. Accordingly, by applying the signal derived from resistance96 to the bases of transistors 84, 86 and 88 via commutation circuit 76,immediate corrective action is effected by rendering these transistorsnonconductive and thereby interrupting the energization of windingstages a, b and c as long as the over-current condition persists. Bysuitably adjusting the settings of regulator 92, the signal derived fromresistance 96 may be caused to take effect at a lower value with respectto the operation of SCR 90 than with respect to its direct applicationto the commutation transistors. Thus, under normal operating conditionsregulator 92 and the SCR will have sufficient time to control motoroperation through the applied voltage V_(M) when an over-currentcondition exists. Control through transistors 84, 86 and 88 is thusreserved for extreme situations only.

Although the circuit illustrated in FIG. 16A, which uses phase controlto control the performance of an ECM, is relatively simple andinexpensive to implement, it is capable of regulating only 120 times persecond for a full-wave rectified 60 Hz signal. This may not be adequatewhere a faster motor response is required. Further, such a circuitreflects a relatively low power factor to the AC line, i.e. less than60%. FIG. 17A illustrates the essential elements of a different type ofcontrol system wherein motor speed regulation is monitored more closelyand power factor correction is provided. As before, applicable referencenumerals have been retained.

As in the circuit of FIG. 16A, diode bridge 70 receives the 115 V, 60 Hzline voltage on a pair of nodes and provides a full wave rectifiedsinusoidal voltage, designated 100 in FIG. 17B, on a second pair ofbridge nodes connected to lines 82, 80. A zero crossing detector andtimer 95 is connected across lines 82, 80, its output being connected toone input of an AND gate 116 in regulator 92. The collector of atransistor 102 is connected to line 82, the transistor emitter beingconnected to a filter 103. A line resistor 110 is connected in seriesbetween line 80 and a line portion designated 80", the latter lineserving as a common voltage reference C. A signal R_(L) is derived atthe opposite terminal of the line resistor. Filter 103 includes acoasting diode 104 connected between the emitter of transistor 102 andline 80", an inductance 106 connected to the emitter of transistor 102,and a capacitor 108 connected between line 80" and the other terminal ofinductance 106, which is connected to a line designated 82' in FIG. 17A.Effective voltage V_(M) appears on line 82' for application to thestator winding stages.

The circuit further includes current shunt 96 connected in seriesbetween lines 80" and 80' and adapted to provide a signal R_(S). Thestator winding stages a, b and c and commutation transistors 84, 86 and88 are connected in the same manner to each other and to commutationcircuit 76 as is shown in FIG. 16A. These components perform theidentical functions in the circuit of FIG. 17A. Likewise, positionsensing circuit 120 is connected and performs in identical manner.

Regulator 92 is seen to comprise an oscillator 112 the output of whichis pulse width modulated by a pulse width modulator 114. Unit 114 iscontrolled by an error detector 97 which receives as inputs the signalsdesignated V_(M), R_(S) and R_(L) respectively. Input C establishes acommon reference level. These input signals are compared against thesignal applied to terminal 93 which is representative of the desiredmotor performance. Thus, the signal applied to terminal 93 is modifiedby signals V_(M), R_(S) and R_(L) to produce an error signal which isapplied to pulse width modulator 114. The output of the pulse widthmodulator is applied to the other input of AND gate 116 whose output iscoupled to the base of transistor 102.

In operation, the commutation action as well as the effect of currentshunt 96, (acting through commutation circuit 76), on the conductivityof transistors 86, 84 and 88, is substantially identical to thatdescribed in connection with the circuit of FIG. 16A. The action ofregulator 92 is different, however. Here, the regulator acts inconjunction with regulating transistor 102 to provide time ratio controlof the applied voltage rather than phase control as was the case in FIG.16A. Specifically, oscillator 112 provides an output signal at apreselected frequency. A frequency range from 20 to 50 KHz is feasibleand 20 KHz is chosen in a preferred embodiment of the invention. Thewidth of the oscillator output pulses is modulated by pulse widthmodulator 114 in accordance with the error signal at the output of errordetector 97, as discussed above. The pulses of varying width are thusapplied to AND gate 116 together with the output of unit 95. If theoutput from unit 95 renders gate 116 conductive, pulses of variablewidth are applied to the base of transistor 102. This action has theeffect of modifying the full wave rectified voltage applied to thetransistor from line 82.

The envelope of the full wave rectified sinusoidal signal on line 82 isrepresented by waveform 100 in FIG. 17B. Reference numeral 101designates the variable width pulses applied to filter 103 fromtransistor 102. It will be clear that neither the true width nor thetrue number of these pulses can be accurately represented in FIG. 17Band the pulses are therefore shown as individual lines only. The currentflowing in the winding stages is shown by waveform 105 in FIG. 17B,which is seen to have substantially rectangular pulses. Thus, errordetector 97 and pulse width modulator 114 constitute means for widthmodulating the voltage pulses to produce substantially rectangularcurrent pulses flowing in the electronically commutated motor, each ofthe rectangular current pulses occurring during a single continuousinterval in each half cycle of the full wave rectified sinusoidalvoltage.

As explained above, pulses are applied to transistor 102 only while gate116 is conductive. It can be shown that the power factor reflected tothe AC line, i.e. to the 115 V, 60 Hz line, is materially improved whenthe third harmonic of the applied waveform is substantially eliminated.Thus, ##EQU6## In order to raise the power factor, I_(RMS) must beminimized. The latter situation obtains when the line current has awaveform which is substantially square or rectangular. Such a waveformis approached if the initial and the final portion of each sinusoidalhalf wave on line 82 are eliminated, while the amplitude of theremaining waveform is maintained substantially constant.

In the embodiment of the invention under discussion, this power factorcorrection feature is implemented in part by permitting gate 116 to beconductive only during a predetermined time interval, e.g. during aphase angle extending substantially from 30° to 150° and from 210° to330° respectively, although it will be understood that the invention isnot limited to these precise intervals. This action, which minimizes thethird harmonic of the rectangular current waveform, is implemented bypermitting transistor 102 to be conductive only during the aforesaidintervals. Thus, the aforesaid pulses of variable width are applied tofilter 103 only during these intervals. This is illustrated in FIG. 17Bwhere waveform 100 is shown in broken lines for the non-conductiveintervals of gate 116.

As explained above, a signal R_(L) derived from line resistance 110 isapplied to error detector 97. This signal takes the form of a voltagereferenced to common voltage level C and varies with the line current.Its effect on regulator 92 is to control the width of the pulses appliedto the base of transistor 102, such that the line current is maintainedsubstantially constant during the conductive intervals, i.e. between aphase angle of 30°-150° and 210°-330° respectively, instead of varyingin amplitude during these intervals in the manner of envelope 100 inFIG. 17B. Coupled with the action of filter 103 which further smoothsout the 120 Hz and 20 KHz ripple of the signal at the output oftransistor 102, the effect of signal R_(L) is to provide a line currentwhose amplitude is substantially as shown by waveform 105 in FIG. 17B.Thus, the combined effect of the feedback action of signal R_(L), thecut-off produced by the output signal of unit 95, and the action offilter 103, is to provide a rectangular-shaped current waveform as shownin 105. Hence, a corresponding improvement of the power factor reflectedto the AC line is achieved.

The effect of applying signals V_(M) and R_(S) to error detector 97 inthe circuit of FIG. 17A is similar to the corresponding action in FIG.16A where signals derived in like manner are applied to regulator 92.Specifically, the application of current shunt signal R_(S) in thecircuit of FIG. 17A results in a variation of the width of the 20 KHzpulses such that the current in the winding stages is decreased when itexceeds a predetermined limit. Similarly, signal V_(M) provides afeedback which is compared against the signal from terminal 93 so as tomaintain the desired angular velocity of the rotatable assembly bysuitably controlling the width of the pulses applied to the base oftransistor 102 and thence to filter 103.

It should be noted that regulation circuit 92 is not limited to theembodiment shown in FIG. 17A. For example, the conversion of the voltagesignal into pulses, i.e. chopping of the signal, may also precede therectifying action of diode bridge 70. Thus, the line voltage may bechopped prior to being applied to bridge 70. Alternatively, chopping maybe carried out by transistor 102 itself, or by a gate turnoff device, orby a controlled rectifier such as an SCR. Other variations within thescope of the invention will readily suggest themselves to those skilledin the art.

While the control system of FIG. 17A is believed to be more complex andmore costly than that shown in FIG. 16A, it is capable of reflecting apower factor greater than 90% to the line terminals and it is thereforea system which has greater energy efficiency. Further, this systemachieves better voltage regulation by monitoring the voltage applied tothe winding stages at the selected frequency of the oscillator, i.e. at20 KHz in the example under consideration. By comparison, the system ofFIG. 16A monitors at only 120 times per second and therefore cannotregulate to the same tolerances. It should also be noted that the powerfactor correction feature shown in FIG. 17A is not limited to ECMcircuits, but may also find application in other motor circuits, as wellas in other circuits where it is important for an electrical load topresent a high power factor to an AC line.

FIG. 18A illustrates another embodiment of a control system for an ECMor for other electrical loads, adapted to reflect a relatively highpower factor to the AC line. As shown, winding stages a, b and c areconnected in a full bridge arrangement which offers certain advantagesover the half bridge connection shown in earlier embodiments, forexample, in FIG. 17A. In the latter circuit the current flows through asingle winding only. In the full bridge connection illustrated in FIG.18A, windings a, b and c have one terminal connected to a point commonto all three windings. Each of the other winding terminals is connectedto a separate junction point 121, 123 or 125 respectively, which joinrespective pairs of commutation transistors 84A, 84B; 86A, 86B; and 88A,88B respectively. Each transistor pair is connected in series acrosslines 82', 80' and each transistor base is connected to receive a signalfrom commutation circuit 76. These commutation signals, designated U, V,W, X, Y and Z respectively, are illustrated in FIG. 18B. The signals aregenerated by unit 76 in response to position signals provided byposition sensing circuit 120, which is connected to receive back EMFsignals V_(a), V_(b) and V_(c).

An advantage of the full bridge connection of the winding stages residesin the fact that motor current flows through a pair of winding stages,e.g. taking a path which comprises line 82', transistor 84A, junctionpoint 121, winding stages a and b, junction point 123, transistor 86Band line 80'. In this circuit, torque is developed more efficiently thanis the case in a half bridge connection where the current flows througha single winding stage only. For a given torque requirement, thedifference may be compensated in the half bridge connection by the useof high-flux permanent magnets in the rotatable assembly. Alternatively,a larger motor may be used with a concomitant increase of the inertia ofthe rotatable assembly. In either case, the cost of the motor isincreased. By contrast, for a given torque requirement the use of a fullbridge-connected ECM permits relatively inexpensive, low-flux, permanentmagnets to be used in the rotatable assembly, with a consequent savingin the total cost of the motor. Where the permanent magnets remain thesame, a smaller, less expensive, low inertia motor may be substituted toprovide the same torque at a cost saving.

Each of commutation transistors 84A, 84B, 86A, 86B, 88A, 88B, has adiode connected thereacross, designated 14A, 14B, 16A, 16B, 18A, 18Brespectively. The purpose of these diodes is to provide alternatecurrent paths for the flow of inductive current through the windingstages when the commutating transistors become nonconductive. Forexample, during commutation transistor 84A may be turned off andtransistor 88A turned on. Such a situation is illustrated in FIG. 18B,which shows the signals applied to the commutation transistors. Asshown, between 60° and 120° signal U is down and signal Y is up.Typically, transistors 84B, 86A and 88B will be cut off at this time,i.e. signals V, W and Z are down. Transistor 86B remains on at thispoint and hence signal X is up. The current path then includes line 80',diode 14B, junction point 121, windings a and b, junction point 123 andtransistor 86B. Thus, the current contributes to the overall torquedeveloped.

In addition to the differences discussed above between the presentcircuit and FIG. 17A, it will be noted that zero crossing detector andtimer 94, line resistance 110 and filter 103 are all eliminated from thecircuit shown in FIG. 18A. The absence of these components in thepresent circuit places the latter at a cost advantage, particularlywhere the filter is concerned. The purpose of filter 103, as explainedabove, is to smooth out the ripples due to the 120 Hz frequency of therectified signal and due to the 20 KHz switching frequency of transistor102. The cost contribution of filter 103 to the overall cost of thecircuit shown in FIG. 17A, excluding the ECM, is believed to berelatively high, rising to as much as 50% of the total circuit cost.Thus, the elimination of the filter circuit alone confers a costadvantage on the circuit of FIG. 18A.

The operation of the present circuit differs from that shown in FIG. 17Ain that no effort is made to switch transistor 102 "on" at the 30° and210° points, or to switch it "off" at the 150° and 330° points. Instead,transistor 102 is operated in a continuous switching mode at theselected frequency, e.g. at 20 KHz. Under these conditions, thetransistor will conduct only when the voltage at its input, i.e. thefull wave rectified sinusoidal voltage applied between lines 82, 80, ishigher than the effective voltage V_(M) between lines 82' and 80'. Noconduction occurs when V_(M) exceeds the line voltage, since the diodesof bridge 70 are back-biased under such conditions.

FIG. 18C illustrates the operation of the circuit shown in FIG. 18A fordifferent operating conditions. Waveform 100 again represents the fullwave rectified sinusoidal voltage on line 82, while waveform 105illustrates motor current flow during the conduction interval oftransistor 102, as sensed by current shunt 96. Waveform 105 is alsorepresentative of the relative amplitudes of V_(M) for the threeoperating conditions illustrated at (1), (2) and (3) in FIG. 18C.

It will be seen that the conduction interval of transistor 102 occurs inthe mid-portion of the sine wave, but that its duration variessubstantially for different operating conditions. Thus, for theoperating condition illustrated at (1) in FIG. 18C, the amplitude of theeffective voltage V_(M) is such that the rotatable assembly turns at anangular velocity which is roughly 25% of the velocity when maximumeffective voltage is applied. The conduction interval of transistor 102,as represented by the duration of current waveform 105, is seen to berelatively long, extending from 10° to 170° in the first half of thecycle and from 190° to 350° in the second half. The operating conditionshown at (3) in FIG. 18C represents the application of the maximumeffective voltage V_(M). Here, the maximum angular velocity isapproximately four times that of the velocity for operating condition(1). The conduction interval is considerably shorter for this operatingcondition, extending only 90° in each half cycle, i.e. from 45° to 135°and from 225° to 315° in the first and second halves respectively, ofthe cycle. Operating condition (2), which lies between the extremes ofconditions (1) and (3), has a conduction interval that extends from 30°to 150° and from 210° to 330° in the first and second halves of thecycle respectively.

It should be noted that the circuit of FIG. 18A, like that shown in FIG.17A, relies on the presence of a current shunt signal R_(S) which isapplied to error detector 97 in order to limit the maximum current inthe winding stages. Further, regulation of the angular velocity ismaintained by feeding back signal V_(M) to an input of unit 97. Both ofthese signals act to vary the width of the pulses applied to the base oftransistor 102, i.e. using time ratio control in a manner similar to thecorresponding action in the circuit of FIG. 17A.

Certain operating factors must be considered which apply to the circuitunder discussion here. For example, under certain operating conditions,e.g. those shown at (3) in FIG. 18C, the peak motor current 105 will betwice the amplitude of the average current. This current flows throughthe winding stages, as well as through commutation transistors 84, 86and 88 and switching transistor 102. Thus, the I² R losses in thewinding stages and in other circuit parts will be doubled during the 90°coduction interval when the peak current flows. Further, the effect ofthe inductance of the winding stages assumes increased significance atthe higher current values and tends to limit current flow. Thus, undercertain conditions a modification of the motor may be required in orderto provide smaller inductance and resistance values in the windingstages.

As stated above, when operating condition (3) occurs and thepeak-to-average current ratio is 2:1, current flows only during thecentral 90° interval in each half cycle. Since torque is developed onlywhen current is present, torque pulsation occurs. While this pulsationis largely smoothed out by the inertia of the rotatable assembly, it maycause a problem under worst case conditions which may limit theeffective operating range of the motor.

It will be understood that the effects of a doubled peak currentamplitude, as discussed above for operating condition (3), can beavoided by the use of a filter, e.g. as shown in FIG. 17A, the effect ofwhich is to average the current. Thus, the price of the cost savingeffected by eliminating the filter is a somewhat poorer performancewhich may, under certain conditions, require circuit or motormodifications. It should be noted, however, that the 2:1 ratio ofpeak-to-average current occurs only under worst case conditions, i.e. atthe maximum angular velocity of the rotatable assembly, when theconduction interval of transistor 102 is 90°. By contrast, under theoperating conditions shown at (1) and (2) in FIG. 18C, the effectsdiscussed above remain within tolerable limits. Thus, for operatingcondition (1), the transistor conduction interval is 160° and the peakcurrent, as well as the I² R losses, increase only by a factor of 1.13over what they would be if a filter were used. Likewise, thepeak-to-average torque ratio is down to 1.13 at this angular velocity.

The elimination in FIG. 18A of line resistance to maintain a constantline current, works, to some extent, against achieving a high powerfactor. However, to the extent that the effective voltage V_(M) remainsconstant, the peak current in the winding stages will also remainsubstantially constant if the load on the motor does not vary. Further,the R_(S) signal provides some regulation of current amplitude and thuscompensates in part for the function otherwise provided by the lineresistance.

It will be clear that the AC line sees a different power factor for eachof the three operating conditions illustrated in FIG. 18C and, in fact,power factor is a continuously changing function for settings of angularvelocity that remain between the extremes shown for operating conditions(1) and (3). The highest power factor values, i.e. above 80%, will occurfor conduction intervals of transistor 102 ranging from 140° at the longextreme to 60° at the short extreme. For conduction intervals which arelonger or shorter, the power factor will fall below 80%. It can be seen,therefore, that the overall power factor throughout the expectedoperating range is relatively high, although not as high as isachievable with the arrangement shown in FIG. 17A. However, since thecost of the filter and of other components is saved in the circuit ofFIG. 18A, the overall cost of the control system, exclusive of themotor, may be reduced by as much as 50%. Thus, the embodiment shown inFIG. 18A may constitute a preferable alternative over other controlsystems.

FIG. 19A illustrates a further embodiment of a control system in whichapplicable reference numerals have been carried forward. As shown,winding stages a, b and c are connected in a full bridge arrangementwith commutation transistor pairs 84, 86 and 88, similar to thecorresponding connection in FIG. 18A. However, transistor 102 isdispensed with in the present embodiment of the invention so that eachtransistor pair is series connected between lines 82 and 80'.

Commutation signals U, V, W, X, Y and Z are substantially identical tothe signals shown in FIG. 18B, being generated by commutation circuit 76in response to the back EMF signals applied to position sensing circuit120 and the resultant position signal applied from the latter circuit tothe commutation circuit. As in FIG. 18A, the bases of transistors 84A,86A and 88A are energized by signals U, W and Y respectively, which areprovided by commutation circuit 76. However, the bases of transistors84B, 86B and 88B are connected to the outputs of corresponding AND gates64, 66 and 68 respectively, each of which has a pair of inputs. SignalsV, X and Z are applied to a first input of gates 64, 66 and 68respectively, while a signal P is applied to the second input of eachgate. A current shunt 96 is connected in series between lines 80 and80'.

Signal P is derived at the output of regulator 92, whose error detector97 compares signal R_(S) and V_(M) against the signal provided fromterminal 93 which is representative of the desired performance of theECM. As in FIG. 18A, the error signal at the output of circuit 97 isapplied to modulator 114, which responds by varying the width of theoutput pulses of oscillator 112. Thus, signal P is a time ratio controlsignal which is provided at the output of unit 114.

It will be clear that the circuit discussed above is not limited to theprecise embodiment shown in FIG. 19A. For example in one form of theinvention, gates 64, 66 and 68 could be connected to the bases oftransistors 84A, 96A and 88A respectively, with signals U, W and Yappropriately applied to one gate input each. In such an arrangement,signals V, X and Z are then applied directly to the bases of transistors84B, 86B and 88B respectively.

In operation, the effective voltage V_(M) is derived from line 82 as afull wave rectified sinusoidal signal. Line 82 applies this signalsimultaneously to commutation transistors 84A, 86A and 88A, each ofwhich becomes conductive when the appropriate commutation signal isapplied to its base. Respective ones of gates 64, 66 and 68 becomeconductive only when the appropriate commutation signal applied to oneinput thereof coincides with the occurrence of signal P which is appliedto the other input. Thus, conductive paths are established in sequence,each including a pair of commutation transistors and a pair of windingstages, as discussed above in connection with FIG. 18A. In the circuitryof FIG. 19A, pairs of electronic devices which comprise commutationtransistors 84A, 84B; 86A, 86B; 88A, 88B and, in FIG. 18A the foregoingcommutation transistors with transistor 102, constitute means forproducing pulses of the full wave rectified sinusoidal voltage during asingle continuous interval in each half cycle of the full wave rectifiedsinusoidal voltage and applying them to the winding stages in at leastone preselected sequence thereby to commutate the winding stages androtate rotatable means, the voltage pulses having a frequency which ishigh with respect to the frequency of the full wave rectified sinusoidalvoltage. In FIG. 17A transistors 102, 84, 86 and 88 also constitute suchmeans. In each of FIGS. 19A, 18A, and 17A error detector 97 and pulsewidth modulator 114 constitute means for width modulating the voltagepulses to produce substantially rectangular current pulses flowing inthe electronically commutated motor, each of the rectangular currentpulses occurring during the single continuous interval in each halfcycle of the full wave rectified sinusoidal voltage.

In the circuit illustrated in FIG. 19A, transistors 84, 86 and 88 areused to commutate as well as to vary the duration of the voltage appliedto the winding stages. Thus, these transistors believed to be used moreefficiently than is the case in the circuits discussed hereinabove andswitching transistor 102 is eliminated. A further advantage of thecircuit shown in FIG. 19A resides in the relatively high power factorwhich is obtainable during the operation of the circuit, provided theangular velocity of the rotatable assembly is limited to a predeterminedvelocity range. This relationship is illustrated in FIG. 19B wherein theAC line power factor is plotted against V_(M) /V_(L) peak. As before,V_(M) is the effective voltage applied to the winding stages which, asexplained above, takes the form of a full wave rectified sinusoidalvoltage in the present circuit. V_(L) peak is the peak AC line voltage.Since V_(M) determines the angular velocity of the motor, the V_(M)/V_(L) peak ratio is velocity-sensitive.

As shown in FIG. 19B, the power factor peaks at approximately 90% whenthe V_(M) /V_(L) peak ratio is about 0.6. It has been determined inpractice that this corresponds to a conduction interval of approximately106, i.e. an operating condition which lies somewhere between conditions(2) and (3) in FIG. 18C. Thus, there is a relatively wide voltage range,and hence a wide range of angular velocity, in which the ECM can beoperated with the control system of FIG. 19A, while reflecting asatisfactory power factor to the line.

The function of the circuits discussed above in connection with FIGS.16-19 is to vary the effective voltage V_(M) applied to the windingstages in accordance with the desired ECM performance represented by thesignal provided at terminal 93. As explained above, this is carried outby varying the duration of the application of the full wave rectifiedsinusoidal signal obtained at the output of the diode bridge. Thefunction of commutation circuit 76 is to apply the aforesaid effectivevoltage to the winding stages of the ECM in a predetermined sequence. Ifthe sequence is repeated, e.g. a-b-c-a-b-c . . . etc., unidirectionalrotation of the rotatable motor assembly in one direction will result.If sequenced a-c-b-a-c-b . . . , unidirectional rotation in the oppositedirection occurs. As discussed above, unidirectional rotation is calledfor during the spin cycle of the laundry machine.

If the commutation circuit alternates the sequence, e.g.a-b-c-a-c-b-a-b-c . . . etc., the rotatable assembly will reversedirections for each alternation of the sequence. The resultantoscillation of the rotatable assembly, e.g. at a frequency of 0.8 Hz ina preferred embodiment of the invention, is required for the wash cycleof the laundry machine. As will become apparent from the discussionbelow, this frequency is selectively variable. It should be noted thatthe ability of reversing the electronically commutated motor by varyingthe sequence in which the winding stages are energized, is in largemeasure responsible for the elimination of the clutch and of the belttransmission required in prior art laundering apparatus where the driveshaft of the laundry machine must be connected and disconnected withrespect to the unidirectional rotation of the induction motor in usewith such machines.

FIG. 24 illustrates in block diagram form a system for controlling theoperation of an electronically commutated motor adapted to drive alaundry machine in accordance with the principles of the presentinvention in one form thereof. The desired motor performance isrepresented by electrical signals which are compared with feedbacksignals representative of actual motor performance to obtain an errorsignal which modifies the duration of a full wave rectified sinusoidalsignal so as to apply a resultant effective voltage to the motor windingstages. Although applicable reference numerals have been retained, itwill be understood that FIG. 24 provides only a schematic overview of apreferred embodiment of the present invention and is not intended tospecify actual connecting lines or the like, even though such lines maybe individually referred to in the discussion below.

Electronically commutated motor 30 is energized from power switchingcircuit 74 and operates in conjunction with rotor position sensor 120which provides a rotor position signal on line 122. In a preferredembodiment of the invention, line 119, which connects motor 30 toposition sensor 120, carries a signal representative of the back EMF ofthe motor, which itself is representative of rotor position, asexplained in greater detail in the aforesaid copending application Ser.No. 802,484. This information is transmitted to decoder 124 by way ofline 122. A further input is applied to the decoder by way of line 135.The latter input represents information regarding the sequencing of themotor windings which controls the direction of rotation, on-offinformation with respect to motor winding energization, step advanceinformation and the like. This data is combined with that received fromposition sensor 120 and is applied to power switching circuit 74 by wayof line 126.

A unit 132 responds to cycle instructions loaded in by the operator ofthe laundry machine to provide appropriate signals on lines 134 and 136for the control of the voltage and current to be applied to the motor,as well as signals which carry the information discussed above inconnection with line 135. The basic functions of unit 132 are those of atimer and of a function generator, as denoted by the blocks designatedby the reference numerals 138 and 140 respectively. While these modulesmay be commercially available, or may be readily constructed fromcommercially available equipment, it is preferred to implement thesefunctions by means of a commercially available microcomputer owing tothe economic advantages of doing so and the ease and flexibility ofhandling information.

Lines 134 and 136 are connected to a unit 142 and apply signals theretorepresentative of the desired motor speed and motor torque. Unit 142performs digital-to-analog conversion of the signals received in digitalform from unit 132. Unit 142 also functions as an error amplifier bycomparing the generated analog signals with feedback received from ECM30. As such, the actual performance of motor 30 is monitored.Specifically, line 144 applies a signal to unit 142 which isrepresentative of the acutal instantaneous angular velocity of therotatable assembly, as represented by the effective voltage V_(M)applied to motor 30. Alternatively, line 144 could apply a signalderived from a speed indicating device, e.g. a tachometer mounted on themotor.

Lines 146 and 148 provide an input proportional to motor current sensedby current shunt 96. Unit 142 acts on the difference between the voltageand current feedback signals and the signals applied by way of lines 134and 136 respectively, to apply an error signal to regulator 92 by way ofline 150. Regulator 92, which here includes SCR 90 if the phase controltechnique discussed in connection with FIG. 16A is used, is fed fromfull wave rectifier 70 and modifies the signal received from the latterby varying its duration. The resultant effective voltage V_(M) isapplied to power switching circuit 74 by way of line 152, to enablecircuit 74 to appropriately control the signals applied to motor 30 byway of lines 156, 158 and 161. Circuit 74 performs the commutationfunction of circuit 76 in FIG. 16A and in other Figures, as well ascertain other functions which will become apparent from the discussionbelow.

A set of switches 128 is selectively actuated by a braking relay 130 andis capable of shorting the winding stages, or placing a low valueimpedance across them, in order to arrest the rotation of the rotatableassembly by the application of a negative torque thereto. The brakingrelay may be actuated from unit 132 in response to action taken by theoperator of the laundry machine. Unit 132 further provides controlsignals by way of lines 163, 165, 167 etc. These lines may control thehot and cold water valves of the laundry machine, the selective couplingof the machine drive shaft to the agitator or to the tub, a display,etc., all coordinated by unit 132 with the signals applied to ECM 30.

In operation, unit 132 responds to the cycle instructions provided atits inputs to apply coded instructions to decoder 124 by way of line 135regarding direction of rotation, motor stepping, on-off data, etc.Similarly, instructions are given to unit 142 by way of lines 134 and136 regarding instantaneously desired motor speed and motor torquerespectively; and to the machine controls by way of lines 163, 165, 167,etc. concerning various information such as water temperature and thelike. Regulator 92 in the circuit under discussion is capable ofreceiving the full wave rectified power signal from unit 70 and ofapplying a D.C. voltage, i.e. effective voltage V_(M), to powerswitching circuit 74 by way of line 152. The amplitude of V_(M) willvary in accordance with the waveforms provided by function generator140. Specifically, the error signal received from unit 142 and appliedby way of line 150, will cause regulator 92 to vary the duration of theapplication of the full wave rectified sinusoidal signal so as to varythe amplitude of V_(M). If the effective voltage is too high, the SCR inregulator 92 will open for a longer time interval in order to lowerV_(M). Conversely, the SCR will open for briefer periods to raise thelevel of V_(M) if a higher motor angular velocity is called for. Ineither case, the signal from regulator 92 is applied to power switchingcircuit 74 by way of line 152. Circuit 74 is further controlled by thesignal received from decoder 124 by way of line 126. The latter signalcontrols the commutation of the windings and the sequence in which theyare energized so as to control the direction of rotation.

Current shunt 96 senses current in the windings which is proportional tothe torque applied by the motor. Thus, the voltage developed acrosslines 146 and 148 is proportional to motor current and is applied tounit 142 where it is compared to the then desired motor current, asrepresented by the signal on line 136. If the actual motor currentexceeds that represented by the signal on line 136, power switchingcircuit 74 is instructed by a signal, applied by way of line 157, toturn off the energization of the winding stages momentarily.Concurrently, regulator 92 is instructed by way of line 150 to regulateto a lower voltage, regardless of the results of the voltage comparisonbetween the signals on lines 134 and 144. This process repeats until themotor current falls below the maximum level set for it. Thus, whenover-current occurs in the motor, i.e. when the motor current risesabove the maximum level set for it, units 74 and 92 are both instructedto take action. The reason for doing so stems from the fact that theaction of regulator 92 may be too slow to cope with the immediacy of aserious over-current situation. However, it will be clear that thissituation arises primarily in the context of a particular implementationof the present invention and that the regulating action could be speededup by a proper choice of suitable design criteria. Alternatively, theregulating action could also occur in the commutating portion of thepower switching circuit, as discussed above in connection in FIG. 19A.Whatever implementation is chosen, it will be clear that,notwithstanding the particular mode of operation selected for theECM-driven laundry machine, the control system is capable of respondingto changing load conditions.

FIG. 21 illustrates an exemplary panel switch arrangement for imposingpertinent control functions on the operation of an ECM-driven laundrymachine in accordance with the present invention in one form thereof.Upon being reset to zero by the actuation of switch 184, subsequentswitch settings will determine the cycle instructions applied to unit132, as explained in connection with the discussion of FIG. 24. Switch160 is an on-off switch which determines the application of power to theECM and other components of the system once the proper instruction isgiven by the microcomputer. The setting of switch 162 causes themicrocomputer to instruct brake relay 130 in FIG. 24 to short the statorwindings by means of switches 128.

The switches shown within the dashed line enclosure designated byreference numeral 164 provide settings that are related to each other,as will become clear from the explanation below. Switch 178 determinesthe applicability of the settings of the related switches to either theforward or the reverse rotation of the agitator. In the presentinvention, motor velocity or torque in opposite directions need not beidentical. Switch 166 determines the applicability of the settings ofthe related switches to the control of either voltage or current,depending on whether it is at a "V LOAD" or an "I LOAD" setting. Thumbwheel switch 168 is capable of selecting by code number one of thewaveshapes shown separately in FIG. 22A. Depending on the setting ofswitch 166, the selected waveshape can apply to either voltage orcurrent, i.e. it will determine the manner in which either the rotorangular velocity, or the motor torque will vary during the selectedstroke. It will be clear that the various waveshapes shown are notexhaustive and that the motion of the agitator and the tube may becontrolled in numerous different ways. The waveshapes designated bycodes 0-5 apply only to the wash cycle, i.e. to the reciprocating actionof the agitator whose angular velocity and torque are controlled inaccordance with the selected waveshape. Codes 6 and 7 apply only to thespin cycle. Switch 170 is capable of selecting by code number themaximum amplitude of the selected waveshape. Depending on whethervoltage (angular velocity) or current (torque) values are involved,preferred ranges of maximum amplitude corresponding to the selected codenumbers are given in the table below:

    ______________________________________                                        VOLTAGE SETTING  CURRENT SETTING                                              Amplitude  Maximum   Amplitude   Maximum                                      Code       Voltage   Code        Current                                      ______________________________________                                        0          15     volts  0         11/4 amps                                  1          30            1         21/2                                       2          45            2         33/4                                       3          60            3         5                                          4          75            4         61/4                                       5          90            5         71/2                                       6          105           6         83/4                                       7          120           7         10                                         ______________________________________                                    

The setting of switch 172 determines whether or not the forward andreverse strokes of the wash cycle will be carried out during time unitsof equal length. For the setting RF=RR, the two time units are identicaland one rate setting suffices. Such a setting is effected by turningRATE FWD potentiometer switch 174 to the desired value which thendetermines the duration of the agitator stroke in both directions. For asetting RF≠RR of switch 172, potentiometer switches 174 and 176 must beseparately set to obtain the appropriate forward and reverse stroke timeunits.

Switch 180 constitutes a scaling switch. The normal rate, as determinedby the setting of potentiometer switches 174 and 176, applies whenswitch 182 is set to "÷1." If it is desired to operate at one-tenth ofthat rate, switch 180 is placed to the "÷10" setting.

Once the settings of the switches discussed above have been made, switch182 is pressed. This action serves to load the information set by eachswitch into unit 132 in the form of the cycle instructions shown in FIG.24.

In order to define the time unit (time interval) required to carry outsuccessive excursions when the rotatable assembly oscillates back andforth, e.g. during the wash cycle, the waveshape selected must besampled periodically as shown in FIG. 22B. For purposes of illustrationonly, the triangular waveshape which corresponds to code 1 in the Tableabove was taken as an example. Sampling is carried out in apredetermined number of steps, 256 steps being used in a preferredembodiment of the invention.

As used herein, the term "sampling" may apply to two different modes ofoperation. When used in connection with a waveshape, e.g. one providedby a function generator, its meaning is to take 256 successive readingsof the amplitude of such waveshape. The values read then jointly definethe waveshape. When the term is used in connection with a control systemthat uses a microcomputer, its meaning is to read out, in succession,stored values which jointly represent the desired waveshape. In eithercase, the sampled values are applied to the winding stages of the ECM inorder to energize the latter.

The rate at which sampling occurs is determined by the settings ofpotentiometer switches 174 and 176, or by switch 174 alone if RF=RR. Fora fixed number of samples, i.e. 256, the faster the chosen samplingrate, the shorter will be the time unit (time interval) during which thefull waveshape is sampled. Thus, the time unit within which eachexcursion of the oscillating rotatable assembly is completed isdetermined by the selected sampling rate. Accordingly, the sampling ratealso bears on the frequency of oscillation.

Owing to the degree of control afforded by the features of the inventiondiscussed hereinabove, certain performance parameters, which are notdirectly controllable, may nevertheless be varied by controlling thoseparameters which underlie them. For example, the displacement angle ofthe agitator is a function of a velocity and time. Since rotor velocityresponds to the applied voltage and since the time interval during whichthe agitator stroke is carried out may be varied by changing thesampling rate, the selection of these two parameters determines theangle of displacement. This is illustrated in FIG. 23A for a sinusoidalstroke corresponding to the waveshape of code 0 in FIG. 22A. Thus, for agiven stroke rate, the selection of the maximum voltage, which isselected by the setting of switch 170, determines the displacement. Aswill be seen from curves 190, 192 and 194 in FIG. 23A, as the maximumvoltage increases a corresponding increase occurs of the maximumpositive as well as maximum negative displacement. This holds also truefor the situation where the maximum applied voltage is held constant andthe rate is decreased.

Similarly, the acceleration rate is adjustable by varying its underlyingparameters. FIG. 23B illustrates this aspect of the present invention.For a given time interval, a change of velocity obtained by varying theamplitude of the applied voltage will result in a variation ofacceleration, as illustrated by curves 196, 200 and 202. The velocity isvaried by selecting the desired maximum voltage amplitude from the tableabove. The variability of acceleration has application not only to bothstrokes of the wash cycle, but also to that portion of the spin cycleduring which the motor comes up to speed.

Before considering the detailed implementation of a preferred embodimentof the present invention, as illustrated and discussed below withrespect to FIGS. 26-39, it will be useful to review the relationship ofcertain component portions of the invention, as shown in FIG. 25, inorder to further an understanding of their function in the overallcontrol system. Thus, FIG. 25 is keyed to the discussion above relativeto FIG. 24. It is pointed out that FIG. 25, while similar to FIG. 16A,is more detailed in some respects, while omitting other portions thatare not pertinent to the particular aspect of the invention underdiscussion here. However, both circuits illustrate a phase-controlledsystem for regulating the voltage applied to the ECM. Wherever possible,applicable reference numerals have been retained.

In the circuit of FIG. 25, 115 V, 60 Hz power is applied by way of inputterminals 210 to a filter 212 which screens out electromagneticinterference and which suppresses transients. Unit 212 comprises a pairof series-connected inductances 215 and 216, and a capacitor 218connected in parallel with a component 220 between the junction point ofinductances 215, 216 and the opposite line. Component 220 is a transientsuppressor of the type which is commercially available from GeneralElectric Company under the designation GEMOV and it functions to apply arelatively pure sine wave to full wave diode bridge 70. The output ofbridge 70 appears on a pair of lines 82 and 80. A silicon controlledrectifier 90 is connected in series with line 82. The line portion onthe far side of SCR 90 is designated 82' for purposes of identification.As was the case in the circuit of FIG. 16A, a full wave rectified DCsignal is applied to SCR 90. A capacitor 78 is connected between lines82' and 80 and provides an essentially ripple-free effective voltageV_(M) to the subsequently connected winding stages.

Motor 30, which may be identical to one of the ECM motors discussed inconnection with FIGS. 3 to 5, includes winding stages a, b and c whichare connected in common to line 82'. The other winding terminals areconnected to switches 128a, 128b and 128c respectively, which may beganged so as to be jointly operable by brake relay 130. Each of switches128 has two positions. In the position shown, the winding stages areshorted across the line. In the second position, winding stages a, b andc are connected in series with the collectors of commutation transistors84, 86 and 88 respectively, whose emitters are connected in common toline 80'. Transistors 84, 86 and 88 have "snubbers" 222, 224 and 226respectively, connected in parallel therewith, for the purpose ofsuppressing transients across these transistors during commutation.Brake relay 130 is connected in series with an optically coupled switch229 which is capable of being selectively turned on and off by anexternal signal. A current shunt 96 is connected in series with line 80'and provides a voltage between the common reference line 146 and line148 representative of current in the winding stages.

Three separate signals designated V_(a), V_(b) and V_(c), which arerepresentative of the back EMF of motor 30 and which are used forposition sensing, are derived at the terminals of winding stages a, band c, which are connected to switches 128a, 128b and 128c respectively.The latter winding terminals are further connected to a set of diodes230, 232 and 234 which form part of an energy dissipation circuit 228.The other diode terminals are connected in common to a line 236. Acapacitor 238 is connected between lines 236 and 82', in parallel withthe series combination of a resistor 240, a transistor 242 and a diode244. A resistor 246 is connected between line 236 and the base oftransistor 242. A resistor 248 is connected in series with a transistor250 between the base of transistor 242 and line 80. The base oftransistor 250 is connected to a terminal 243.

To the extent that the operation of the circuit shown in FIG. 25 followsthat discussed above in connection with the operation of FIG. 16A, norepetition is required. It will be clear that SCR 90 in the circuit ofFIG. 25 is turned on upon the application of a suitable signal to itsterminal 91. Such a signal is generated at a phase angle, i.e. at a timeinterval following a zero crossover of the line voltage, which isdetermined by the particular conditions such as speed, torque, etc.,which are being regulated.

In the energy dissipation circuit 228, transistor 250 is normallymaintained in a conductive state by the application of a suitable signalto its base from terminal 243. When transistor 250 is conductive,transistor 242 is biased into a conductive state, as determined by thedivision of voltage between resistors 246 and 248. Under theseconditions, the voltage across capacitor 238 is regulated to the samevalue as the effective voltage V_(M) applied to the winding stages.Whenever a winding stage is switched during the commutation process, theenergy stored in the inductance of the winding stage must be dissipated.The dissipation path includes the diode connected to the switchedwinding and capacitor 238. Thus, capacitor 238 is charged through diodes230, 232 and 234 by the energy stored in the inductance of the windingstages during normal commutation. Between these successive commutations,the capacitor discharges through a series path comprising resistor 240,transistor 242 and diode 244, and thus dissipates the stored energy. Theexcess energy is dissipated directly in the path which comprisesresistors 246 and 248 and transistor 250 on the one hand, and resistor240, transistor 242 and diode 244 on the other hand.

As will become clear from the explanation below, the signal applied toterminal 243 is proportional to the error voltage which ultimatelydetermines whether the motor is to speed up or slow down. At apredetermined level of this voltage, indicative of excessive motorspeed, this signal is applied to terminal 243 and causes transistor 250to cut off. The full voltage which appears across winding stages a, band c is therefore applied to the base of transistor 242 and causes thelatter to turn on to its maximum extent. In consequence, maximum energydissipation now takes place in the network branch which comprisesresistor 240, transistor 242 and diode 244. The energy so dissipatedexceeds the amount of energy which is required to be dissipated due tocommutation alone. As a consequence, the rotor encounters a drag whichslows down its speed of rotation. In essence, a low impedance issubstituted for the relatively high impedance previously connectedacross the motor windings, but only as required by the particularsituation. The increased drag or negative torque on the rotatableassembly comes into effect automatically as required, i.e. energydissipation is increased when needed. Thus, the control system respondsautomatically to the existing circuit operating conditions.

The above-described feature of the invention is superior to merelylowering the effective voltage applied to the motor, since it can actmore decisively and quickly than a system which depends primarily on thedrag torque during coasting of the rotatable assembly. This property ofthe present control system is particularly valuable in a laundrymachine, e.g. for slowing down the agitator preparatory to a reversal ofrotation during its oscillatory motion. In the absence of specialcircuitry, the agitator will have a tendency to coast if it is sloweddown merely by lowering V_(M). While it would be possible to short themotor winding stages, or even to reverse them, the resultant agitatoraction may be undesirable since it may damage the wash load. Bycomparison, the dynamic braking feature of the present invention, whichcomes into effect automatically as required, is believed to providegentle handling of the wash load.

FIGS. 26 to 39 illustrate in one form of the invention implementation ofthe control system shown in block diagram form in FIG. 24 and which wasfurther explained with reference to FIG. 25. It is pointed out thatFIGS. 26-39 illustrate an actual implementation of the presentinvention. Hence, the organization and discussion of these Figuresfollows the physical location of various circuit components on thedifferent circuit boards used, i.e. in accordance with the actualimplementation of the control system. It will be understood, however,that the invention is not so limited and that the same components may bearranged in a different organizational plan without departing from theprinciples of the present invention.

To the extent that they are applicable, previously used referencenumerals have been retained. The reference letters and numbers shownwithin a circle in the drawings designate terminals on different circuitboards. It is pointed out that terminals which are marked with the sameletters or numbers in the different Figures are not electricallyconnected to each other except as specifically described. Theinterconnection of these terminals is shown in detail in Appendix "A"and is further clarified in the description that presently follows. Inthe specification, the aforesaid reference letters are called out assuch; however, reference numbers which apply to terminal connection areshown underlined to distinguish them from the reference numerals bywhich various circuit components are designated.

FIG. 39 illustrates the interconnections of various circuit componentsand terminals of FIG. 25 discussed below, as well as circuitryimmediately connected to these terminals.

A 115 V, 60 Hz power line input is applied across terminals F, H and J,K, of FIG. 39, which are further connected to full wave diode bridge 70.Lines 80 and 82 couple the output of bridge 70 to terminals B, C and D,E respectively. A filter comprising a resistor 676 and a capacitor 218is connected across terminals B, C and D, E, ahead of bridge 70, for thepurpose of suppressing transients. Terminals F, H are further coupled toterminal V, which itself is connected to optically coupled switch 229,identical to that shown in FIG. 25. Device 229 is coupled to a terminalW which is further connected to the brake coil relay 130, e.g. as shownin FIG. 25.

A pair of optical couplers 680, 682, is connected in series with aresistor 684 across terminals X and Y. Terminals X and Y are furtherconnected to the output of unit 132 in FIG. 24, which comprises amicrocomputer in the preferred embodiment of the invention. Althoughdifferent types of commonly available microcomputers may be employed, itis preferred to use a PLS 858 unit, as described in Appendix B, which iscommercially available from Prologue Corp. of California. Thus, abraking command from the microcomputer, e.g. in response to actuation ofswitch 162 in FIG. 21, is transmitted to the brake by way of theaforesaid optical couplers. This arrangement isolates the computer tokeep its ground reference inviolate.

The terminal connections shown in FIG. 39 further include terminals L, Nand R connected to diodes 230, 232 and 234 respectively, which arelikewise shown in FIG. 25. These diodes are coupled to a common line 236which is connected to a terminal S. Line 236 is also connected to aterminal U by way of a pair of capacitors 238A and 238B which jointlysubstitute for capacitor 238 in FIG. 25.

FIG. 26 illustrates a low voltage power supply which provides regulatedpower for the microcomputer employed in the control system herein. Theprimary winding of a transformer 260 is connected across a pair ofterminals L and N of FIG. 26 and receives 115 V, 60 Hz power. A pair ofdiodes 262 and 264 is connected to opposite terminals of the transformersecondary. The free diode terminals are jointly connected to line 270 toprovide a full wave rectified signal at the latter. A capacitor 266 isconnected between lines 270 and 272, the latter line being coupled to atap, preferably the midpoint, of the transformer secondary winding.Thus, 11 V peak of DC voltage appears across capacitor 266 whichprovides a filtering action to eliminate ripple. A regulator 268 iscoupled to lines 270 and 272. A potentiometer 274 is connected acrossthe output of regulator 268 and is capable of adjusting the voltageprovided at the output. A capacitor 276 is connected acrosspotentiometer 274 and provides filtering of the 5.0 V regulated DCoutput voltage provided between a pair of output terminals S and R ofFIG. 26.

FIG. 36 illustrates another low voltage power supply which provides 10.0V DC across a pair of output terminals U and T. The power supply shownin FIG. 36 is substantially similar in construction to that illustratedin FIG. 26. Its function is to provide a regulated voltage for variouscircuits discussed below, primarily for the operational amplifiers andfor the logic circuits. A transformer 280 has its primary windingconnected across a pair of terminals K and M of FIG. 36 to which the 115V, 60 Hz power line is connected. A pair of diodes 282 and 284 isconnected to opposite terminals of the transformer secondary. The freediode terminals are connected to line 290 to provide a full waverectified signal across a ripple capacitor 286. Capacitor 286 isconnected between lines 290 and 292, the latter line being connected toa tap, preferably at the midpoint of the transformer secondary. Thus, 17V peak DC is applied across capacitor 286. This voltage is furtherapplied to a series regulator 288 connected between lines 290 and 292. Apotentiometer 294 is connected between the output of regulator 288 andcommon line 292 and is adjustable so that its output voltage may beregulated to 10.0 volt D.C. applied across a pair of output terminals U,T of FIG. 36. This voltage is referred to as V_(r) in the drawings andhas been so indicated in FIG. 36. A filter condenser 296 is connectedacross the aforesaid output terminals. The secondary winding oftransformer 280 is further connected to a pair of terminals R and P ofFIG. 36 so as to apply 12 V RMS, 60 Hz between each terminal and commonline 292. Information relating to zero crossovers on the AC line appearsat these terminals for subsequent application to the circuit shown inFIG. 30 which is discussed below.

The circuits illustrated in FIGS. 32 and 37 are substantially identical,each providing a variable frequency oscillator for sampling, at a chosenrate, the particular waveshape that was selected from the set ofwaveshapes shown in FIG. 22A. Sampling occurs as explained in connectionwith FIG. 22B. FIG. 32 illustrates the circuit used for varying the ratein the forward direction in accordance with the setting of potentiometer174, as discussed in connection with FIG. 21. The potentiometer iscoupled to a pair of terminals T and S of FIG. 32, which are furtherconnected to an oscillator 684 by way of a series-connected resistor686. The frequency of the oscillator is determined by the setting ofpotentiometer 174, sometimes referred to as a potentiometer switch inthe discussion of FIG. 21. A capacitor 688 is connected between resistor686 and a further input of oscillator 684. Other input terminals ofoscillator 684 are connected to voltage V_(r) and ground respectively,as shown in the drawing.

Output 690 of oscillator 684 is coupled to the base of a transistor 700by way of a resistor 692. The transistor emitter is coupled to groundand its collector is connected to an optical coupler 694, which isfurther connected to receive reference voltage V_(r) by way of aresistor 698. One output terminal of optical coupler 694 is connected toa terminal of FIG. 32 which is further coupled to the microcomputer. Thesame output terminal of the coupler is further connected to a +5 voltlevel by way of a resistor 696, the other coupler output terminalreceiving -5 volt.

In FIG. 37, potentiometer 176 is set as described above in connectionwith the discussion of FIG. 21. Potentiometer 176 is connected acrossterminals 18 and 17, the latter terminals being directly connected to aninput of an oscillator 702. Terminal 18 is coupled to the oscillatorinput by way of a resistor 704. A capacitor 706 is connected between thelatter resistor and a further input terminal of oscillator 702. Otheroscillator inputs are connected to a pair of terminals T and Mrespectively, as shown in FIG. 37, the latter terminal being tied toground. A pair of capacitors 708 and 710 are connected in parallelbetween terminals T and M of FIG. 37, capacitor 710 serving as ahigh-frequency bypass around capacitor 708.

The frequency of oscillator 702 is determined by the setting ofpotentiometer 176. The oscillator output 712 is coupled to the base of atransistor 716 by way of a resistor 714. The emitter of transistor 716is grounded, its collector being connected to an optical coupler 722whose input is further connected to a terminal T of FIG. 37 by way of aresistor 718. The output terminals of coupler 722 are connected to apair of terminals P and Z of FIG. 37 resepctively. The side connected toterminal P of FIG. 37 is further connected to a terminal Y of FIG. 37 byway of a resistor 720.

The operation of the circuits of FIGS. 32 and 37 is substantiallyidentical and will therefore only be described for the former circuit.The setting of rate potentiometer 174 determines the frequency of thesignal obtained at output 690 of oscillator 684. This signal isamplified by transistor 700 and is coupled to microcomputer 132 (in FIG.24) by way of terminal R of FIG. 32. As explained above, optical coupler694 maintains the microcomputer isolated. The frequency of the incomingsignal is used by the microcomputer to sample the selected waveshape inthe forward direction of the rotor. Thus, the setting of rate controlpotentiometer 174 acts through the microcomputer to determine thesampling rate of the selected waveshape and hence the duration anddisplacement of the agitator stroke in the forward direction. Thesetting of rate potentiometer 176 has the same effect for the reversestroke of the agitator.

FIG. 27 illustrates a preferred implementation of a scaling circuit forscaling the rate selected by potentiometer 174. The scale selection ismade by switch 180 in FIG. 21, as explained above. A signal is appliedto a terminal J of FIG. 37 at a particular oscillator frequency, thelatter being determined by the settings of rate potentiometer switch 174in FIG. 21. The incoming signal is applied to a divider 300 whose outputis connected to one leg of a NAND gate 302. A terminal K of FIG. 27 isconnected to the other leg of NAND gate 302, as well as to both inputsof a NAND gate 306. The latter gate has its output connected to oneinput of a NAND gate 308. A further input of gate 308 is connected toreceive the incoming signal directly from input terminal J of FIG. 27.The output of gate 308 is connected to one input of NAND gate 304,another input of the latter being connected to the output of gate 302.The output signal of the circuit is derived at the output of gate 304which is connected to a terminal H of FIG. 27.

In operation, a signal generated by the setting of switch 180 in FIG. 21is applied to terminal K of FIG. 27. If the waveshape selected fromthose shown in FIG. 22A is to be sampled at the normal rate, i.e. therate determined by the settings of switch 174 in FIG. 21, the signalapplied to terminal K of FIG. 27 renders gate 308 conductive by way ofgate 306. Accordingly, the oscillator signal applied to terminal J ofFIG. 27 is transmitted by gate 308 and thus reaches terminal H of FIG.17 by way of NAND gate 304. If, on the other hand, scaling by a factorof 10 is to take place, the signal applied to terminal K of FIG. 27 whenswitch 180 is set, renders gate 302 conductive. Accordingly, theoscillator signal is applied to frequency divider 300 and a signalhaving one-tenth the frequency of the oscillator signal is transmittedby way of gates 302 and 304 to output terminal H of FIG. 27, forsubsequent coupling to the microcomputer.

FIG. 28 illustrates preferred implementation of the digital-to-analogconverter and error amplifier unit for the applied motor voltage, shownat 142 in FIG. 24. The regulated DC voltages supplied by the circuits ofFIGS. 26 and 36 discussed hereinabove, i.e. +5 volt and V_(r)respectively, are applied to terminals B and D of FIG. 28, respectively.In the preferred embodiment of the invention shown, eight opticalcouplers 310 are employed, which are powered from the aforesaidregulated DC voltages. As before, the optical couplers serve to isolatethe microcomputer from the rest of the control system in order to keepthe computer at a true ground reference. In each instance, the terminaldesignated by a letter numeral and shown in a circle in FIG. 28,represents one of the eight digit input lines from the computer whichare collectively designated by the reference numeral 134 in FIG. 24. Thecorresponding output terminal in each case, designated by the sameletter but with a bar above it, is connected to the D/A converterproper. Thus, the 8-bit computer input is received on terminals J, K, L,H, N, P, R and M of FIG. 28, while the corresponding signals which areapplied to the D/A converter itself appear at terminals J, K, L, H, N,P, R, and M of FIG. 28 respectively.

As shown, the latter set of terminals is connected to a pair ofelectronic switching units 312 and 314 respectively, each having fourterminals which are appropriately designated J, K, L, H and N, P, R, Malso in FIG. 28, respectively. Voltage V_(r) is coupled to switchingunit 312 by means of resistors 501, 503, 505 and 507, each having adifferent value. Depending on which of terminals J, K, L and H receive asignal to acutate the appropriate switch contacts, none, one, or more ofresistors 501, 503, 505 and 507 respectively, will be connected inparallel between voltage source V_(r) and the common output of switchingunit 312. The latter is further connected to an input leg of anoperational amplifier 316. Accordingly, the level of the signal appliedto amplifier 316 will depend on the 4 bit code applied to terminals J,K, L and H to provide digital-to-analog conversion. Similarly, switchingunit 314 provides a signal level at its common output which depends onthe 4 bit code applied to terminals N, P, R and M.

Connected as shown, amplifier 316 is adapted to provide a gain. Tostabilize its output signal, a feedback is placed around the gain stageby means of resistor 317. The output of amplifier 316 is coupled to ajunction point 321 by means of a resistor 319, whence it is combinedwith the output of electronic switching unit 314 and is so applied toone input leg of a summing amplifier 318. The latter has a feedback pathcoupled between its output and another input leg thereof, comprising aresistor 323 connected in parallel with a capacitor 326. Thus, at theoutput of amplifier 318 a voltage is provided which is proportional inamplitude to the 8 bit binary number applied by the microcomputer to theinput terminals of optical couplers 310. This voltage is coupled to oneinput leg of an amplifier 322 by way of a variable resistor 335connected in series with a fixed resistor 337.

The voltage V_(M), which is applied to the common connection of thewinding stages, (see FIG. 25), is applied to terminal 9 of FIG. 28. Fromthere, it is coupled to an input leg of an amplifier 320 by way of aresistor 325 connected in parallel with the series combination of acapacitor 327 and a resistor 329. The output of amplifier 320 is fedback to a second input leg by way of a resistor 331 connected inparallel with a capacitor 333, to provide a forward gain factor of 0.05in a preferred embodiment of the invention. Thus, the motor voltage isscaled down to be compared by amplifier 322 with the output signal ofamplifier 318. The output of amplifier 320 is coupled to another inputleg of amplifier 322 by way of a resistor 339, as well as to an outputterminal 11 of FIG. 28 at which the scaled down motor voltage can beobserved directly. The output of amplifier 322 is coupled to thelast-recited input leg of amplifier 322 by way of a parallelresistor-capacitor combination 341, 343. Voltage V_(r) is resistivelycoupled to both input legs of amplifier 322. The signal which resultsfrom the comparison of the outputs of amplifiers 318 and 320, i.e. theerror signal, appears at an output terminal 12 of FIG. 28, which iscoupled to the output of amplifier 322. This is an analog signal whichis proportional to the difference between the actually applied motorvoltage and the motor voltage called for by the microcomputer.

FIG. 29 illustrates a preferred implementation of the D/A converterportion of unit 142 in FIG. 24 which applies to motor current only andwhich receives its computer input signal by way of line 136 in FIG. 24.In similar manner to the circuit shown in FIG. 28, optical couplers 330couple an 8 bit digital signal received from the microcomputer by way ofterminals W, Y, Z, X, S, U, V, T, of FIG. 29, to corresponding terminalsW, Y, Z and X on electronic switching unit 332 and to terminals S, U, Vand T on electronic switching unit 334, of FIG. 29 respectively.Digital-to-analog conversion is provided through the signal level at theoutput of each switching unit, which depends on the 4 bit code appliedat the input terminals. The output of switching unit 332 is applied to again stage 336 whose output is coupled, by way of a resistor 345, to oneinput leg of a summing amplifier 338, jointly with the output of unit334. The feedback loop of amplifier 338, connected between its outputand a second input leg, includes a variable resistance 347 in parallelwith a capacitor 349. The signal which appears at a terminal 13 of FIG.29 is thus proportional in amplitude to a maximum current permitted bythe 8 bit digital signal applied by the microcomputer to the inputterminals of optical couplers 330.

The comparison of the signal appearing at output terminal 13 in FIG. 29with a signal representative of actual motor current is carried out inthe circuit shown in FIG. 31. it will be understood that the signalprovided at terminal 13 in FIG. 29 is an analog signal representative ofthe maximum permissible current for a given setting of potentiometerswitch 170 in FIG. 21. This signal is coupled to terminal W in FIG. 31,for application to a comparator 410 by way of a resistor 411. Acapacitor 412 is connected to ground from the aforesaid input terminalof comparator 410 and is adapted to filter out transient voltage surges.Voltage V_(r) is coupled directly to a further input of comparator 410and, by way of a resistor 413, to the output of unit 410. The output ofunit 410 is connected to terminal V.

A voltage proportional to motor current, which is derived across currentshunt 96 in FIG. 38 discussed below, is applied to a pair of terminals Xand Y in FIG. 31. The latter terminals are coupled, by way of resistors415 and 417, to input legs 414 and 416 respectively, of an amplifier418. The output of amplifier 418 is coupled back to input leg 414 by wayof a pair of parallel resistors 419 and 421 in order to provide greatersignal stability. Voltage V_(r) is applied to input leg 416 by way of anetwork 420. The latter includes a resistor 423 connected to a junctionpoint 422. A pair of resistors 425 and 427 is connected in parallelbetween the latter junction point and input leg 416. Point 422 isfurther connected to ground through a pair of series connected diodes429, as well as through a capacitor 433 connected in parallel with thediode pair. The output of amplifier 418 is coupled to a further inputleg of comparator 410 by way of a resistor 435. A capacitor 437 isconnected between the last recited input leg and ground.

In operation, the voltage across terminals X and Y, of FIG. 31 which isrepresentative of actual current in the winding stages, is compared byunit 410 to the analog voltage appearing at terminal W of FIG. 31representative of the maximum current called for by the microcomputer,i.e. as applied by line 136 in FIG. 24. The result of this comparison isan error signal which appears at a terminal V of FIG. 31 and which isapplied to a one shot multivibrator 424 by way of terminal N in thecircuit of FIG. 35 discussed below. The output of a one shot 424 appearsat a terminal 10 in FIG. 35, whence it is coupled to a terminal 14 inFIG. 30 and is subsequently applied to comparator 350, as discussedbelow. In essence then, the circuit shown in FIG. 31 performs thefunction of comparing the voltage across current shunt 96, which isrepresentative of actual motor current, with the signal applied toterminal W of FIG. 31 from the circuit of FIG. 29, which represents themaximum motor current set by the microcomputer.

A more elaborate technique for using phase control is employed in thecircuit illustrated in FIG. 30 which shows the use of a ramp andpedestal technique for controlling the SCR. The error voltage derived atterminal 12 in FIG. 28, which represents the difference between thevoltage called for by the microcomputer and that actually applied tomotor 30, is applied to terminal J in FIG. 30. Terminal J is connected,by way of a resistor 351, to one input leg of an operational amplifier350 which functions as a comparator in the present circuit. The voltageV_(r) is resistively coupled to another input leg of comparator 350, byway of a juncton point 376. The 8 V RMS, 60 Hz voltage, obtained atterminals R, P in FIG. 36, is applied to terminals F, H, of FIG. 30whence it is full wave rectified by diodes 352 and 354 and is applied,by way of resistors 353 and 355, to one input leg of an amplifier 356. AZener diode 358 which is connected between ground and the junction point360 of resistors 353 and 355, serves to regulate the voltage applied toamplifier 356 to 6.8 volts in a preferred embodiment of the invention.Voltage V_(r) is resistively coupled to another input leg of amplifier356.

Junction point 360 is coupled by way of a pair of resistors 362 and 364to the input leg of comparator 350 to which the error signal fromterminal J of FIG. 30 is applied. Resistors 362 and 364 are joined at ajunction point 366 which is connected to ground by way of a capacitor368. A resistor 299 couples the output of amplifier 356 to the base of atransistor 370 whose emitter is directly connected to ground. Thecollector of transistor 370 is connected to junction point 366 by way ofa diode 372 and a resistor 374 connected in series therewith.

As discussed above, the signal at terminal 10 in FIG. 35 is coupled toterminal 14 in FIG. 30, from where it is applied to junction point 376by way of a network 378 connected in series with a resistor 357 at afurther junction point 380. Network 378 includes a resistor 359connected in parallel with a resistor-diode series combination 347, 363,between junction point 380 and terminal 14. A filter capacitor 381 isconnected between junction point 380 and ground. The purpose of network378 is to obtain a fast rise--slow decay response to a signal appearingat terminal 14 upon the occurrence of excess current in the windingstages.

Amplifier 350 has a feedback resistor 361 connected between its outputand junction point 376 which provides positive feedback forstabilization during switching. The latter output is further connectedto one input leg of a NOR gate 382, whose other input leg is connectedto the output of amplifier 356. The output of gate 382 is coupled to anoscillator circuit 386 by way of a further NOR gate 384. Oscillatorcircuit 386 takes the form of an astable multivibrator and comprises aNOR gate 388 having a first input leg connected to the output of gate384. A second input leg of this gate is connected to the output of afurther NOR gate 390, by way of a capacitor 392 and a resistor 394. Theoutput of gate 388 is connected to the jointly connected input legs ofgate 390, as well as to a resistor 396 whose other terminal is connectedto the junction point of capacitor 392 and resistor 394.

The output of gate 390 is coupled, by way of a resistor 365, to the baseof a transistor 398 whose emitter has the aforesaid reference voltageV_(r) applied thereto. The collector of transistor 398 is connected tothe primary winding of an output transformer 400 whose secondary windingis connected to a pair of terminals L and K of FIG. 30. A resistor 401is connected across terminals L, K of FIG. 30. As shown elsewhere in thedrawings in FIGS. 38 and 25, terminals L, K of FIG. 30 are connected toapply a signal to SCR 90.

Terminal J of FIG. 30, which receives the aforesaid error signalrepresentative of the difference between the voltage called for by themicrocomputer and, that which is actually applied to the winding stages,is further coupled to one input leg of a comparator 402 by way of a pairof resistors 367, 369, whose junction point is coupled to ground througha capacitor 371. The output of comparator 402 is coupled throughresistor 373 to the aforesaid input leg to provide positive feedback forstabilization during switching. Reference voltage V_(r) is resistivelycoupled to a second input leg of comparator 402. The comparator outputis coupled to an output terminal C of FIG. 30 through a resistor 375. InFIG. 25 the latter terminal corresponds to terminal 243 in energydissipation circuit 228.

As previously explained in conjunction with the discussion of FIGS. 16Aand 25, the regulation of the voltage applied to the winding stages ofmotor 30 controls the angular velocity of the motor. By means of phasecontrol the time interval during which SCR 90 is conductive is varied.This is done by choosing the point in time, i.e. the phase angle of theapplied sine wave, at which the normally non-conductive SCR is turnedon. The voltage appearing at the output of the SCR is filtered so that arelatively smooth effective voltage V_(M) results, the amplitude ofwhich varies with the interval of conductivity of the SCR. By increasingthe time interval during which the SCR conducts, the effective voltageV_(M) applied to the winding stages is increased and the motor angularvelocity increases. By decreasing the conductivity period of the SCR,motor angular velocity is decreased.

The ramp and pedestal technique illustrated by the circuit of FIG. 30enhances the effectiveness of phase control by providing greaterstability. As implemented herein, this technique depends on theapplication of a reference voltage to the comparator together with aramp signal, i.e. with a linearly increasing voltage which is started ata determinable point in time. In the present invention, this point istaken at the zero crossover point of the full wave rectified line signalwhich is applied at the input of amplifier 356. When the line voltageapplied across terminals F, H of FIG. 30 goes to zero, operationalamplifier 356, which compares this signal to reference voltage V_(r),turns on. By this action transistor 370 is turned on and causescapacitor 368 to discharge to ground through the path established byresistor 374, diode 372 and transistor 370. The signal appearing at theoutput of amplifier 356 is further applied to the input of NOR gate 382in order to lock the latter, i.e. to render it nonconductive. Theresultant signal across terminals L, K of FIG. 30 is applied to the SCRand prevents triggering of the latter.

As the full wave rectified line voltage appearing at junction point 360rises beyond a pre-established value, the output of amplifier 356 goesto zero and transistor 370 is cut off. At this point, the RC circuitformed by resistor 362 and capacitor 368 causes the latter to chargefrom the line, i.e. from the signal appearing at junction point 366.Accordingly, there is a rise of the voltage at junction point 366 andthus a rise of the voltage applied to the connected input leg ofcomparator 350. At such time as the voltage on the last-recited inputleg of comparator 350 exceeds the voltage applied to the other inputleg, the comparator turns off and its normally high output signal goesto zero.

The error signal applied to terminal J of FIG. 30, which is derived fromterminal 12 in FIG. 28, changes polarity depending on whether thevoltage applied to the motor is too high or too low, indicative of motorover-speed or under-speed respectively. This signal, which isresistively coupled to one input leg of comparator 350, thus either addsor subtracts from the ramp voltage applied to the same input leg. Whenit adds to the ramp voltage, comparator 350 turns on sooner and causesthe SCR to be conductive for a longer time interval. The effective V_(M)applied to the stator windings is thereby increased so as to raise theangular velocity of the motor. The opposite is true if the error signalsubtracts from the ramp signal applied to comparator 350. In the lattercase, the comparator turns off at a later point in time and the SCR isconductive for a shorter time interval. As a consequence, a smallereffective voltage is applied to the winding stages and the angularvelocity of the motor decreases.

As discussed above, terminal 14 of FIG. 30 is connected to receive asignal from terminal 10 in FIG. 35. The signal so applied is indicativeof excessive current in the winding stages and is added to the appliedreference voltage V_(r) to increase the "pedestal" voltage applied tocomparator 350. Thus, the voltage difference between the two inputs ofcomparator 350 is decreased and hence the comparator turns off at alater point in time. The effect is the same as that discussed above inconnection with an error signal which decreases the applied rampvoltage. Specifically, comparator 350 turns off at a later point in timeand the effective V_(M) applied to the stator windings of motor 30 isdecreased. The result is to decrease motor angular velocity until themotor current falls below its pre-set maximum level.

In order to couple the output signal of comparator 350 to SCR 90 viatransformer 400, the signal is first applied to astable multivibrator386 which provides an output signal at a frequency of 10 KHz in thepreferred embodiment of the invention. The oscillator output signal ispower-amplified by transistor 398 and is applied to the primary windingof transformer 400. The output signal appearing across terminals L, K ofFIG. 30 then serves to turn on the SCR at the desired phase angle.

From the foregoing explanation it will be apparent that the circuit ofFIG. 30 is capable of responding to changing load conditions bycontrolling the operation of motor 30 in accordance with pre-selectedvoltage and current values. Whichever of these quantities reaches itspreselected limit first will be the regulated quantity. For example, ifduring a particular motor operation the motor current never reaches themaximum limit set for it, motor speed will follow the voltage waveshapeselected from those shown in FIG. 22A. However, if the maximum motorcurrent is exceeded while following the selected voltage waveshape,motor angular velocity will be decreased regardless of the selectedwaveshape until the motor current, (torque applied by the motor), fallsbelow the maximum value. Similarly, for a selected maximum applied motorvoltage, i.e. for a selected maximum angular velocity of the motor, themotor operation will follow the selected current waveshape only as longas the maximum motor voltage is not exceeded.

FIG. 33 illustrates a preferred embodiment of position sensor 120 shownin block diagram form in FIG. 24, as well as other circuitry requiredfor electronic commutation of the motor windings. Portions of thecircuit herein are similar to the commutation circuit disclosed in theaforesaid copending application Ser. No. 802,484, now U.S. Pat. No.4,169,990, incorporated by reference herein. As disclosed in the latterapplication, the back EMF generated in successive winding stages ofmotor 30 is detected in each stage during the interval when that stageis not being energized, i.e. when V_(M) is not applied thereto. In eachinstance the detected back EMF is processed to determine the position ofthe rotor relative to the stator. A simulated output signalrepresentative of relative rotor position is generated by means of whichthe successive energization and deenergization of winding stages a, band c respectively, is effected.

Voltage V_(M) which is applied to the ECM, is provided at terminal J inFIG. 33. V_(M) is coupled to a first junction point 430 through aresistor 432; to a second junction point 442 through a pair ofseries-connected resistors 438 and 440; and to ground through a resistor444. Junction points 430 and 442 are thus at a reduced voltage levelwith respect to terminal J of FIG. 33 due to the action of the voltagedivider constituted by the aforesaid resistors. Voltage V_(r) is appliedat terminal D of FIG. 33 and is coupled to a junction point 434 via aresistor 436 and then to junction point 430 via a resistor 431.

Junction point 442 is connected to one input leg of a differentialamplifier 446 which has an adjustable resistor 448 connected theretoadapted to set the amplifier bias at a selected level. A feedbackresistor 450 is connected between the output of amplifier 446 and asecond input leg, the latter being further coupled to the contact pointsof an electronic switching device 452. Each variable contact ofswitching device 452 is coupled to ground by way of a pair ofseries-connected resistors 454 and 456, a common junction point 460 anda network 462. The latter comprises a pair of capacitors 464 and 466 anda diode 468 connected in parallel with each other between junction point460 and ground. The connecting point between each pair of resistors 454and 456 is further connected to a resistor 458. Back EMF's V_(a), V_(b)and V_(c), generated by winding stages a, b, and c respectively, areapplied to the other terminal of respective resistors 458. Each networkcomprising resistors 454, 456 and 458 acts as a voltage divider to scaledown the levels of the back EMF's applied to the variable contacts ofswitching unit 452.

The application in FIG. 33 of one or more of signals S_(a), S_(b), S_(c)whose derivation in FIG. 34 is discussed below, closes the appropriatecontact of electronic switching unit 452 and applies the correspondingscaled-down back EMF signal to the second input leg of differentialamplifier 446. As explained above, amplifier 446 further receives ascaled-down effective voltage V_(M) on its first input leg.

The output signal from differential amplifier 446 is coupled by way of aresistor 472 to a variable contact 474 of an electronic switching device478. Depending on the signal at the output of a NOR gate 498, contact474 is either connected to, or disconnected from, a first input leg ofan amplifier 470. A second input leg of the amplifier 470 is connectedto junction points 434 and 460. The output of NOR gate 498 is coupled tothe jointly connected inputs of a further NOR gate 480. The output ofgate 480 controls a second variable contact 476 of switching unit 478,which is adapted to connect to, or disconnect from, ground the firstinput leg of amplifier 470.

A capacitor 482 and a Zener diode 484 are connected in parallel betweenthe output of amplifier 470 and its first input leg. Thus connected,amplifier 470 operates to integrate the signal applied to its firstinput leg which represents the difference between the applied motorvoltage V_(M) and the back EMF. The Zener diode functions to preventintegration of a negative signal value. Integration is thereforeinitiated when the difference between the two voltages goes through zeroin a positive direction. Zener diode 484 also functions to determine thevoltage at which capacitor 482 is reset, i.e. charged, prior to thestart of the integration process.

The output of amplifier 470 is coupled to a first input of a comparator488 by way of a resistor 486. A pair of further inputs of comparator 488is tied to ground, while a fourth input taps a portion of voltage V_(r)which is applied across a variable potentiometer 490. Voltage V_(r) iscoupled directly to a further input of comparator 488. The output 494 ofcomparator 488 is coupled to one input leg of the aforesaid NOR gate498, to potentiometer 490 by way of a resistor 492, and to voltage V_(r)by way of a resistor 496.

The integrated signal from amplifier 470 is compared at the comparatorinput against the voltage tapped off from potentiometer 490, which maybe selectively varied. When the signal applied from amplifier 470reaches a reference level corresponding to a predetermined number ofvolt-seconds, comparator 488 produces a high level logic signal atoutput 494. Whenever the integrated voltage signal falls below theaforesaid reference level, comparator 488 produces a low level outputsignal, as determined by the setting of potentiometer 490.

As stated above, the reference level at which comparator 488 provides ahigh level output signal corresponds to a predetermined number of voltseconds and hence it indicates that a predetermined rotor positionrelative to the stator windings of motor 30 has been reached. These highlevel output pulses are used to commutate the winding stages of themotor in the preferred embodiment of the invention under discussion. Thepoint in time at which the high level output pulses occur is adjustableby means of potentiometer 490 and is selected to provide an advancedtiming angle, i.e. a predetermined amount of commutation advancement. Asdiscussed in greater detail in the aforesaid copending application Ser.No. 802,484, now U.S. Pat. No. 4,169,990, zero advancement is said toexist when a winding stage is turned on at the point where the magneticcenter of the rotor-established polar region is a predetermined numberof electrical degrees from alignment with an axis of a magnetic poleestablished by energizing the winding stage and when it is moving towardthe latter. In the example under consideration, this angle is 150electrical degrees. Switching the winding stage before the zero advanceposition is reached, provides advancement of commutation and allows thecurrent built up in the winding stage to achieve the maximum possibletorque throughout the time interval during which the winding stage isenergized. In the present invention this is accomplished by the settingof potentiometer 490.

Comparator output 494 is further coupled to a one-shot multivibrator byway of a series-connected capacitor 502 and a resistor 504 connectedbetween capacitor 502 and ground. The one-shot comprises a NOR gate 500which has one input leg connected to the junction point of elements 502and 504. The other input leg of gate 500 is connected to a countercircuit 506 as well as to the output of a further NOR gate 508. The oneshot further includes a capacitor 510 connected in series between theoutput of NOR gate 500 and the commonly connected input of NOR gate 508.Voltage V_(r) is coupled to the input of gate 508 by way of a resistor512. The output of gate 508 is further connected to a second input legof NOR gate 498.

The signal from the output of NOR gate 500 is coupled to a first inputleg of a NAND gate 514. A further input of the latter gate receives asignal from the output of a counter circuit 506, by way of a capacitor516. The aforesaid voltage V_(r) is resistively coupled to thelast-recited gate leg. The output of gate 514 is applied to a firstinput of a flip flop circuit 518. A second input leg of this flip flopis designated by the reference numeral 520. A first output leg 522 offlip flop 518 is coupled to an output terminal at which the flip flopoutput signal A of FIG. 33 is provided. Logically inverted signal A isprovided at a second flip flop output leg designated 524. The aforesaidfirst output is further connected to a first input leg of another flipflop 526. A second input leg 527 is connected in common with input leg520 of flip flop 518. Signals B and B of FIG. 33 are provided at a pairof outputs of flip flop 526, designated 528 and 530 respectively.

Signals A and B are applied to the respective inputs of a NOR gate 532which is connected to another one shot multivibrator comprising NORgates 536 and 544. The output of gate 532 is connected to one input legof gate 536 by way of a series-connected capacitor 538 and a resistor540 connected between the aforesaid input leg and ground. Another inputof NOR gate 536 is coupled to the output of NOR gate 544. The commonlyconnected inputs of gate 544 are coupled to the output of gate 536 byway of a capacitor 542. Voltage V_(r) is coupled to the inputs of gate544 by way of a resistor 546. The output of gate 544 is furtherconnected to flip flop inputs 520 and 527.

The output of NOR gate 500 which provides a signal representative ofrotor position is connected to the commonly connected inputs of a NANDgate 548. The output of gate 548 is connected to the base of atransistor 550 by way of a resistor 552. The emitter of transistor 550is grounded and its collector is connected to an optical coupler 554which receives the aforesaid reference voltage V_(r) by way of resistor556. One output terminal of optical coupler 554 is directly connected toa terminal K of FIG. 33 and, by way of a resistor 558, to a terminal F.The other coupler output terminal is connected to a terminal H, also ofFIG. 33. Thus, the signal which indicates that the rotatable assembly isin commutation position and hence ready to commutate, is coupled back tothe microcomputer through terminals K and H of FIG. 33.

A counter circuit 506 comprises a counter 560 which has an outputconnected to capacitor 516 and a reset input connected to the output ofNOR gate 508. Counter 560 also receives voltage V_(r) at an inputthereof, while a further input is connected to a junction point 562which joins the output of a first NAND gate 564 to the commonlyconnected inputs of a second NAND gate 566. The output of the lattergate is connected to a further junction point 568 by way of a capacitor570. Junction point 568 is connected to the commonly connected inputs ofNAND gate 564 by way of a resistor 572. A resistor 574 connects junctionpoints 562 and 568.

In operation, when the high logic level output signal of comparator 488is applied to the one shot multivibrator comprising NOR gates 500, 508and RC combination 510, 512, a signal is produced at the output of gate500 which is applied to subsequently connected circuitry for the purposeof commutating the winding stages. Further, the corresponding logicallyinverted output signal of gate 508 is applied an input leg of NOR gate498 to produce a signal that changes the setting of variable contact 474in switching unit 478. The last-recited signal also causes the resultantoutput signal of gate 480 to change the setting of variable contact 476.At the new switch settings, the integrator constituted by amplifier 470and the parallel connection of capacitor 482 and Zener diode 484, isreset by charging capacitor 482. The new setting of switches 474 and 476is further effective to lock out the signal derived at the output ofamplifier 446 and prevent it from being integrated during commutation.

The signal derived from the one-shot multivibrator, whether taken at theoutput of gate 500 or taken in logically inverted form at the output ofgate 508, is representative of a predetermined position of the rotatableassembly. In addition to the described functions of this signal, i.e. toreset integrator capacitor 482 and to lock out the signal from unit 446during commutation, the signal also performs the functions of selectingthe next winding stage to be energized; initiating the deenergization ofthe presently energized winding stage; and the selection of a subsequentunenergized winding stage for the purpose of detecting its back EMF.These selection functions are accomplished through the flip floparrangement provided by units 518 and 526 and their associated one-shotmultivibrators. The flip flops provide the aforesaid signals A, A, B ANDB which, before carrying out the selection process, are further decodedas described below in connection with the discussion of FIG. 34.

Under ordinary conditions, flip flops 518 and 526 act as a countertogether with the associated one shot comprising NOR gates 536 and 544and with NOR gate 532. This counter counts to 3 to response to signalsderived at the output of gate 514 and then resets to 0. The resettingaction is initiated by NOR gate 532

As previously explained, commutation occurs by way of the commutationtransistors 84, 86 and 88 which are connected to winding stages, a, band c respectively. See FIGS. 25 and 38. The back EMF is used to senserotor position, as explained above in connection with FIG. 33, in orderto energize the windings in sequence. This is carried out by means ofsignals S_(a), S_(b) and S_(c) which are developed when the rotatableassembly is turning, as explained in connection with the discussion ofFIG. 34 below. However, when the motor is at a standstill, e.g. uponstart up, no back EMF is generated. Depending on the position of therotatable assembly at standstill, three possibilities exist with respectto the selection of the next winding stage to be energized or, moreprecisely, with respect to turning on the connected commutationtransistor. These are as follows:

(1) The correct winding stage was selected, i.e. the winding stage whichwould be next energized if the rotor were turning in the selecteddirection;

(2) The wrong winding stage was selected, i.e. the winding stage whichwill cause the rotor to turn in the reverse direction from thatselected; or

(3) A winding stage was selected which, because of the rotor position,provides no torque and hence the rotor fails to turn.

Situation (1) above presents no problem. In large measure this islikewise true for situation (2) because of the fact that someEMF--albeit the incorrect signal--is generated and serves as a referencesignal. Thus, the motor will start up in the wrong direction, but willreverse almost immediately.

Circuit 506 provides a timing function which permits the motor to starteven if situation (3) obtains. Specifically, if a high level signal isnot applied to NOR gate 500 from output 494, the output signal of gate500, which is applied to a first input of gate 514, will be ONE.Accordingly, a ZERO signal must be applied to the other input of gate514 in order to obtain the requisite ONE signal at its output so thatthe aforesaid resetting action can be initiated. This is accomplished byapplying the output signal of NOR gate 508 to the reset input 561 ofcounter 560. If a ZERO signal is applied from NOR gate 500 to the inputof NOR gate 508, it will result in the application of a ONE signal toinput 561 of counter 560. This signal initiates the counting sequence ofcounter 560 at a rate determined by the frequency of the oscillatorconstituted by NAND gates 564 and 566 and their associated circuitry.When a predetermined count is reached, a ZERO output signal is appliedby way of capacitor 516 to the other input of NAND gate 514. Theresultant ONE signal at the output of the latter gate then initiates thecounting sequence of flip flops 518 and 526. This has the effect ofapplying the motor voltage V_(M) to the next winding stage in thesequence and rotation of the rotatable assembly is initiated. Duringnormal commutation, counter 560 is reset upon each commutation, butbefore a predetermined count has been reached. The predetermined countis representative of the maximum amount of time permitted betweencommutations. Under normal operating conditions this count, whichindicates a stalled condition, is never reached. Therefore, countercircuit 506 comes into play only when a stalled condition exists andotherwise has no effect on the operation of the control circuit.

Signals S_(a), S_(b) and S_(c), which are applied to electronicswitching unit 452 in FIG. 33, are developed from output signals A, A, Band B generated by the circuit illustrated in FIG. 33. The logic circuitfor providing signals S_(a), S_(b) and S_(c), for both the forward andthe reverse rotation of the rotor, is shown in FIG. 34. Themicrocomputer is coupled to an optical coupler 580 by way of a pair ofterminals F, S of FIG. 34, a resistor 582 being connected betweenterminal S of FIG. 34 and the coupler. Reference voltage V_(r) isapplied to the output of the optical coupler by way of a resistor 584,while the other output terminal is grounded.

The output of optical coupler 580 provides a Forward/Reverse signal inresponse to a computer command received at terminals S, F of FIG. 34.The computer command in turn is responsive to the setting of switch 178,as discussed in connection with FIG. 21. The Forward/Reverse signal iscoupled to the forward section of a decoder where it is applied to oneinput leg of each of NAND gates 586, 588 and 590 respectively. The term"forward section" refers to a circuit portion concerned exclusively withthe forward rotation of the rotor. Gate 586 further receives theaforesaid signals A and B of FIG. 33 on separate input legs thereof;gate 588 receives the signals A, B of FIG. 33; and gate 590 receives thesignals A, B of FIG. 33.

The output of optical coupler 580 is connected to the commonly connectedinputs of a NAND gate 592. The output of gate 592, which constitues the"Reverse" signal, is connected to one input leg of each of a set of NANDgates 594, 596 and 598 respectively, which form the reverse section ofthe decoder. NAND gate 594 further receives signals A, B at its inputs;gate 596 receives signals A, B; and gate 598 receives signals A, B, allof FIG. 33. The outputs of gates 590 and 594 are applied to a NAND gate600 which provides signal S_(a) at its output. Gates 588 and 596 areconnected to the inputs of NAND gate 602 which provides the signal S_(b)at its output. Gates 586 and 598 are connected to the inputs of a NANDgate 604 which provides the signal S_(c) at its output.

In operation, the signal applied from the microcomputer to terminals S,F of FIG. 34 actuates either the forward or the reverse section of thedecoder. The signals A, B, A and B, which are successively generated inthe same sequence at the output of the circuit of FIG. 33, are appliedto the inputs of gates 586, 588, 590, 594, 596 and 598. Depending onwhether the forward or the reverse section of the decoder is active, thedecoder output signals will either be generated in the sequence S_(a),S_(b), S_(c), or in the sequence S_(a), S_(c), S_(b). As previouslyexplained, these signals are then applied to the individual switches ofelectronic switching unit 452 in FIG. 33 which functions to apply theback EMF's of the connected winding stages to differential amplifier446.

FIG. 35 illustrates a preferred decoding circuit for controlling theenergization and deenergization respectively, of the winding stages.Here again, a section of the logic circuitry shown is devoted todecoding for forward rotation of the rotatable assembly and a separatesection is devoted to reverse rotation. The Forward signal, derived atthe output of optical coupler 580 in FIG. 34, is applied to one inputleg of each of NAND gates 606, 608 and 610 respectively. Similarly, theReverse signal derived at the output of gate 592 in FIG. 34, is appliedto an input leg of each of NAND gates 612, 614 and 616 respectively.Signals S_(a), S_(c) and S_(b), which are developed as discussed abovein connection with the circuit of FIG. 34, are applied to the inputs ofgates 606, 608 and 610 respectively. Gates 612, 614 and 616 receivesignals S_(c), S_(a) and S_(b) respectively, at their inputs.

A NAND gate 618 is connected to the outputs of gates 610 and 612 andprovides an output signal to a further NAND gate 624. A NAND gate 610 isconnected to the outputs of gates 608 and 614 and has its own outputcoupled to one input of a NAND gate 626. A NAND gate 622 is connected tothe outputs of gates 606 and 616 and has its own output connected to oneinput of a NAND gate 628. Each of gates 624, 626 and 628 furtherreceives a pair of inputs from the output of a NAND gate 630 and fromthe output of an optical coupler 632. The latter output is furtherconnected to receive voltage V_(r) by way of a resistor 634. The inputof coupler 632 is connected to terminal S of FIG. 35 by way of aresistor 636 and directly to a terminal M of FIG. 35 to receive ON/OFFinstructions from the microcomputer. The latter responds to the settingof switch 160, as explained in connection with FIG. 21.

Voltage V_(r) is applied directly to a number of inputs of the earliermentioned one-shot multivibrator 424 and to other input terminals ofunit 424 by way of resistors 638 and 640 respectively. Resistors 638 and640 are further connected to capacitors 642 and 648 respectively, eachof which is coupled to its own input terminal on unit 424.

As previously explained in connection with FIG. 31, one-shot 424 isactivated from terminal N of FIG. 35 when the motor current exceeds themaximum value set by the microcomputer. Further, as explained above, theoutput 650 of unit 424 is connected to terminal 10 of FIG. 35. Thelatter terminal is further coupled to terminal 14 in FIG. 30 which isconnected to the ramp and pedestal circuit illustrated there. Output 650is also coupled to the commonly connected inputs of NAND gate 630.

The outputs of NAND gates 624, 626 and 628 are coupled to the bases ofcorresponding driver transistors 652, 654 and 656 respectively, by wayof resistors 658, 660 and 662 respectively. The emitters of the lattertransistors are connected in common to a terminal P of FIG. 35. Thecollectors of transistors 624, 626 and 628 are connected to a set ofthree terminals R, U and X of FIG. 35 respectively, by way of resistors654, 666 and 668. As will be explained in greater detail below inconnection with the discussion of FIG. 38, the signals applied toterminals R, U and X are effective to control the switching of thecommutation transistors which are connected in series with the windingstages of the motor.

In operation, when the motor current exceeds the maximum value set bythe microcomputer, as discussed in connection with FIG. 31, the signalapplied to terminal N of FIG. 35 causes one-shot 424 to apply an outputpulse to the input of NAND gate 630. The resultant output signal fromgate 630 is NANDED by gates 624, 626 and 628 with the decoded positionsignals and with the ON/OFF instruction signal from the microcomputer.The resultant output signals from these gates are applied in sequence todriver transistors 652, 654 and 656 and render the latter conductive forthe duration of the multivibrator pulse. This action serves to applycorresponding signals to terminals R, U and X of FIG. 35 adapted toactivate the commutation transistors.

FIG. 38 illustrates a preferred implementation of the power controlcircuit for motor 30 for use with the circuit of FIG. 25 discussedabove. A 13 of FIG. 38 receives the full wave rectified line voltagefrom the output of diode bridge 70, which is further applied to SCR 90.The control voltage is applied to the SCR by way of terminal 16 of FIG.38 and is derived from one of terminals L or K in FIG. 30. The output ofthe SCR is applied to a terminal 17, of FIG. 38 as well as to energydissipation circuit 228. The latter circuit is physically located onseveral circuit boards in the preferred embodiment of the invention andtherefore appears only in part in FIG. 38. Its function, discussed inconnection with FIG. 25, remains the same.

When SCR 90 is closed, the full wave rectified line signal applied toterminal 13 of FIG. 38 is coupled to a high gain amplifier by way of adiode 244. The high gain amplifier comprises a first transistor 242Aconnected in series with diode 244, and a second transistor 242B havingits emitter connected to the base of transistor 242A. The collectors ofboth transistors are connected in common through resistor 240 to aterminal 19 of FIG. 38. Terminal 19 of FIG. 38 is connected to terminalS in FIG. 39 and thus, through common line 236, to diodes 230, 232 and234. Energy dissipation circuit 228 is completed by capacitors 238A and238B, which are connected in parallel between line 236 and terminal U ofFIG. 39. The latter terminal is coupled to terminal 17 in FIG. 38. Aresistor 246 is connected between the base of transistor 242B and lline236. The aforesaid transistor base is further connected to the collectorof a transistor 250 by way of a resistor 248. The base of transistor 250is connected to a terminal 7 of FIG. 38 which is coupled to terminal Cin FIG. 30. The emitter of transistor 250 is connected to line 80, inseries with the aforesaid current shunt 96. The voltage developed acrossresistor 96 appears across output terminals 24 and 12 of FIG. 38, whichare further coupled to terminals X and Y in FIG. 31.

Capacitor 78, which serves to filter the voltage at the output of SCR 90in FIG. 25 is seen to be connected between terminals 17 and 24 of FIG.38 and it provides an essentially ripple-free effective voltage V_(M) tothe winding stages.

A set of terminals 11, 10 and 9 of FIG. 38 are connected to thecollectors of commutation transistors 84, 86 and 88 respectively.Terminals 23, 22 and 21 of FIG. 38, which are coupled to the bases ofthese transistors, are further connected to terminals R, U and Xrespectively, in FIG. 35. Hence, the action of power transistors 652,654, 656 in FIG. 35 controls the action of the corresponding commutationtransistors 84, 86 and 88 respectively, whose emitters are connected incommon to line 80.

As explained in connection with the discussion of FIG. 25, snubbingcircuits 222, 224 and 226 are provided to suppress transients. In apreferred embodiment of the invention, each snubbing circuit comprises aparallel combination of a resistor 670 and a diode 674, connected inseries with a capacitor 672 between the collector of the correspondingtransistor and line 80. For the sake of simplicity, the components ofsnubbing circuit 222 only have been detailed in the drawings, it beingunderstood that snubbing circuits 224 and 226 are substantiallyidentical to circuit 222.

To place the circuit shown in FIG. 38 in its proper context, it will beunderstood that terminals 11, 10 and 9 of FIG. 38 are coupled toterminals L, N and R respectively in FIG. 39. Further, terminal 11 ofFIG. 38 is connected to switch 128a shown in FIG. 25, which connects towinding stage a. Similarly, terminal 10 is connected to switch 128bwhich is further connected to winding stage b. Terminal 9 is connectedto switch 128c, the latter being further connected to winding stage c.

As previously explained in connection with the discussion of FIG. 24,unit 132 receives cycle instructions and communicates with decoder 124;with D/A converter and error amplifier 142; and with the controls of thelaundry machine. In carrying out these tasks, unit 132 acts essentiallyin the capacity of a function generator and timer. In the preferredembodiment of the invention these functions are performed by amicrocomputer of the type shown in Appendix B. Other commerciallyavailable computer capable of carrying out these functions may besubstituted.

When acting in the capacity of a function generator, the microcomputercan select a variety of different waveshapes, such as shown in FIG. 22A,or others that may be stored in memory in digital form. By way ofexample, Appendix C is a printout in hexadecimal form of the informationactually stored in the ROM of the aforesaid microcomputer in a preferredembodiment of the invention. This information is called up by making useof the sampling technique described hereinabove. The values called upfrom memory jointly represent the selected waveshape from among thoseshown in FIG. 22A.

The timing function performed by the computer clocks the wash and spincycle. Various other timed operations of the laundry machine areperformed under microcomputer timing control, such as the number ofrinsings to be used, the tub filling cycle, etc., which are, however,beyond the scope of the invention herein. The microcomputer receivescommands in the form of cycle instructions. These cycle instructions areeffective to select a particular speed and torque waveshape, to selectthe maximum values of applied voltage and current respectively, toselect the rate of the agitator stroke, etc.

To illustrate the operation of the apparatus disclosed herein for thewash and the spin cycle respectively, two examples are given. For abetter understanding, reference should be made to the control panel andthe waveshapes illustrated in FIGS. 21 and 22 respectively, and toTables D and E above.

WASH CYCLE

Let it be assumed that during the wash cycle the agitator is to followthe speed profile given by waveshape code 0 FIG. 22A, i.e. a sinusoidalwaveform. Further, the maximum applied voltage is to be 90 V, equivalentto amplitude code 5 in Table D above. Maximum torque is to correspond toamplitude code 3 in Table E, i.e. maximum current is to be 5 amps.Finally, the agitator is to have the same speed profile in the forwardand reverse directions, as well as the same forward and reverse rate.

For the assumed conditions the operation will perform the followingsteps:

A. Set switch 160 to "OFF."

B. Set switch 162 to "ON."

C. Press switch 184 to reset the microcomputer.

D. Load "reverse" instructions for voltage (speed) using the followingsub-steps:

(1) Set switch 178 to "Reverse."

(2) Set switch 166 to "V LOAD."

(3) Set switch 170 to "5."

(4) Set switch 168 to "0."

(5) Set switch 172 to "RF=RR."

(6) Press switch 182 to load information set under D(1)-D(5) into thecomputer.

E. Load "forward" instructions for voltage (speed) as follows:

(1) Set switch 178 to "Forward."

(2)-(6) Repeat steps D(2)-D(6).

F. Load "Reverse" instructions for current (torque) using the followingsub-steps:

(1) Set switch 178 to "Reverse."

(2) Set switch 166 to "I LOAD."

(3) Set switch 170 to "3."

(4) Set switch 168 to "5."

(5) Set switch 172 to "RF=RR."

(6) Press switch 182 to load information set under F(1)-F(5).

G. Load "Forward" instructions for current (torque) as follows

(1) Set switch 178 to "Forward."

(2)-(6) Repeat steps F(2)-F(6).

H. Set Potentiometer switch 174 to desired rate. (Varying setting ofswitch 174 as desired during operation.)

J. Set switch 180 to "÷1."

K. Set switch 162 to "OFF."

L. Set switch 160 to "ON."

SPIN CYCLE

Let it be assumed that the maximum ramp speed is to correspond to amaximum voltage of 120 V. The maximum torque is to correspond to acurrent limit of 10 amps. The ramp rate is to be 1/10 of normal.

For the assumed conditions, the operation will perform the followingsteps:

A. Set switch 160 to "OFF."

B. Set switch 162 to "ON."

C. Press switch 184 to reset microcomputer.

D. Load "Forward" instructions for voltage (speed) as follows:

(1) Set switch 178 to "Forward."

(2) Set switch 166 to "V LOAD."

(3) Set switch 170 to "7."

(4) Set switch 168 to "7."

(5) Set switch 172 to "RF=RR."

(6) Press switch 182 to load D(1)-D(5).

E. Load "Forward" instructions for current (torque):

(1) Set switch 178 to "Forward."

(2) Set switch 166 to "I LOAD."

(3) Set switch 170 to "7."

(4) Set switch 168 to "6."

(5) Set switch 172 to ∓RF=RR."

(6) Press switch 182 to load E(1)-E(5).

F. Set potentiometer switch 174 is desired rate.

G. Set switch 180 to "÷10."

H. Set switch 178 to "Forward."

J. Set switch 162 to "OFF."

K. Set switch 160 to "ON."

L. To brake the spin, set switch 162 to "OFF."

As previously explained, in a washing machine of the type employed forhome use, certain parameters of the foregoing operating parameters willnot be individually selected, but rather automatically, e.g. inaccordance with the type of fabric to be washed, the size of the washload, or the like, all as selected by the user. Thus, for a particulartype of fabric, a certain agitator speed may be appropriate, possiblyone which is different for the forward and reverse directions. In anyevent, a pre-selected voltage profile will be stored in memory for sucha fabric. Likewise, for the same fabric a certain torque profile may bedesired. Here again, a particular pre-selected current profile will bestored in memory. The user of the machine however, will select primarilyby fabric and wash load, although he may have the option of overridingthe preselected profile in order to tailor machine performance moreclosely to actual needs.

The operation of the programmed microcomputer, which is used in thepreferred embodiment of the invention in lieu of a timer and functiongenerator, is illustrated by the flow chart in FIG. 40A. Appendix Dreproduces the applicable computer program in machine language.

With reference to FIG. 40A, it will be understood that the various stepsshown there and discussed below, result from the action taken by theoperator of the laundry machine, as described above in conjunction withFIGS. 21 and 22. Accordingly, reference is made below to the pertinentdrawing Figures. It will be further understood that the particularmicrocomputer used with the preferred embodiment of the invention willhave various registers, as well as memory capacity, for the temporaryand permanent storage of data, all as shown in Appendix B. For example,the various waveshapes shown in FIG. 22A may be permanently stored inmemory, a shown in Appendix C in hexadecimal form. Among other functionsperformed is the task of keeping track of the number of points, (out ofa total of 256), that have been sampled on the selected waveform. SeeFIG. 22B. A storage register of the microcomputer, hereinafter referredto as the L register, is used for this operation.

In initializing the microcomputer, all registers and memories, exceptthose that contain data in permanent storage, are reset to 0. Thiscommand may be issued by the microcomputer in response to the actuationof the reset switch 184, or it may occur in response to other eventsbeyond the scope of this discussion. The initializing command isrepresented by block 730, which is seen to be connected to block 732 byway of a nodal point 736. If switch 178 was set to a particularposition, i.e. Reverse or Forward, a bit is set in the microcomputerupon initialization, as shown by block 732. The bit so set isrepresentative of the selected direction of rotation.

Once the aforesaid bit is set, a check is made by the microcomputer todetermine whether or not the brake switch 162 was set to "ON." Thisaction is illustrated by decision block 734. If switch 162 was set, themicrocomputer provides instructions for setting the brake and forturning off the motor, all as indicated by block 746. As further shownby block 748, the computer then instructs the regulator to regulate to 0voltage and 0 current, indicative of a stand still condition. A loadcheck is made, as shown by decision block 750, to determine whether ornot load button 182 was pressed. If not, the aforesaid L register isreset by 0 by the microcomputer, as indicated by the path from block 750to block 756, via nodal point 754. Block 756 is connected back to nodalpoint 736, indicative of the fact that the routine can now be repeated.If the load button was in fact pressed, block 752 indicates that thecomputer instructs the circuit to load the waveshape which waspreviously selected by means of switches 170 and 168, into the computermemory. Here too the L register must be reset to 0, as indicated by thepath from block 752, via block 756, to nodal point 736.

Before the operation can begin, a further check must be made concerningthe status of switch 160. Specifically, if the brake was found to beoff, decision block 738 determines the status of switch 160. If theswitch was turned to the "OFF" position, the microcomputer issuesinstructions to turn the motor off, as indicated by block 740. Further,the regulator is instructed by the microprocessor to regulate to 0voltage and 0 current and the L register is reset to 0, all as shown byblock 742. Block 742 is seen to be connected to nodal point 736,indicative of the fact that the routine can now be repeated.

It will be understood that the check concerning the status of switches162 and 160 may be interchanged in time. However, the arrangement shownin FIG. 40A was selected as being the more convenient one to implement.

If during the next iteration of the routine switch 160 was turned on, asindicated by the appropriate output of decision block 738, themicrocomputer issues instructions for the motor to be turned on and forsetting its direction of rotation. The latter actions are indicated byblock 762. At this point, decision block 764 checks to determine thedirection that was set for the rotor. This decision is made on the basisof the bit previously set, as explained in connection with block 732.Assuming the reverse direction of rotor rotation was set, block 766indicates the presence of a microprocessor instruction to implement theselection of the waveshape for either voltage or current, (depending onthe setting of switch 166), in accordance with the previous operatorsetting of thumb wheel switch 168. Specifically, the appropriateinformation is now called up from the stored look-up table shown inAppendix C. Simultaneously, the microcomputer issues instructionsconcerning the maximum amplitudes of the motor voltage and currentselected by means of switch 170.

The reverse rate set by potentiometer switch 176 is now called up undermicrocomputer instruction, together with the scale determined by thesetting of switch 180, with respect to the motor voltage and motorcurrent respectively. These actions are indicated by blocks 768, 770 and772. The values so called up are temporarily stored. Similarly, if theforward direction was selected, the waveshape determined by the settingof switch 168 is called up from computer storage, together with theselected maximum amplitudes set by switch 170, the forward rate set bypotentiometer switch 174 and the scale applied for both the voltage andthe current by switch 180. These actions are indicated by blocks 776,778, 780 and 782 respectively. Again, the data regarding scaling istemporarily stored.

Nodal point 774 indicates that the procedure is henceforth the same,regardless of the selected direction of rotation. Block 784 shows thatthe stored, scaled voltage and current quantities are now sent out tothe D/A converters, as explained previously in this specification.Thereafter a check is made in accordance with block 786, to determinewhether or not the final sampling point on the selected waveshape hasbeen reached. In the preferred embodiment herein, this is the 256thpoint. If the answer is "no", the L register is incremented by One, asindicated by block 794. As shown, block 794 is positioned between a pairof nodal points 792, 796. A return path extends from the latter pointback to point 758. This return path indicates an iterative routine.Specifically, each time the L register is incremented a check is made ofthe microcomputer response to the status of brake switch 162 and ofON/OFF switch 160, to determine whether or not such status remains thesame.

The process continues until the last point on the selected waveform hasbeen sampled. At that time, as shown by decision block 788, themicrocomputer determines whether or not the waveshape is one indicatedby waveshape codes 6 or 7, both of which call for a non-reversing actionof the agitator. See FIG. 22A. If the latter waveshapes were notselected, a microprocessor instruction is issued to apply a "Reverse"signal to the motor, as shown by block 790. The latter block is seen tobe connected to nodal point 792 and thus to block 794. This pathposition indicates that the final point on the selected waveform wasreached and the selected waveform was not one indicated by codes 6 or 7.Thus, the waveform calls for agitator oscillation and the direction ofthe motor is reversed. Incrementing of the L register at this timecauses it to overflow and reset automatically to zero. A check is againmade regarding the status of switches 160 and 162.

If the 256th point on the waveform was reached and code 6 or 7 wasselected, the L register is not incremented. Since codes 6 and 7 applyonly to the spin cycle, the action continues in accordance with the spinduration interval, which is set by a separate timing mechanism. However,as shown by the schematic connection of decision block 788 to nodalpoint 796 and thence to nodal point 758, a check of the status of thebrake switch and of the ON/OFF switch is made at this time.

As will be apparent to those skilled in the art, the method of operatingthe microcomputer is not limited to that shown by the flow chartillustrated in FIG. 40A and that it may be performed and implemented ina number of different ways consistent with the principles of the presentinvention. Any such variations will of course be reflected incorresponding changes of the machine language program of Appendix D.

As previously explained, for ordinary household use laundering apparatusbuilt in accordance with the present invention may contain fabric andwash load panel selection switches in place of the switches shown inFIG. 21. For each fabric/wash load combination, there will exist apre-programmed wash cycle and a pre-programmed spin cycle, possibly withthe option to override and set independently. Thus, the operationindicated in block 760, outlined in broken lines in FIG. 40A, may bereplaced by that contained in the like-numbered block of FIG. 40B.

As indicated by block 800, initially a selection is made of the fabricto be washed and of the wash load. The microcomputer responds to theselection by an inquiry regarding the status of switches 162 and 160, asindicated by blocks 734 and 738 in FIG. 40B. This is similar to theaction shown in FIG. 40A. If the brake was off and the ON/OFF switch isturned on, a particular wash and spin routine is selected frommicrocomputer storage. This is shown by block 804. If the brake was onand/or the switch was on, other action beyond the scope of thediscussion herein may be taken by the laundry machine, e.g. a suitabledisplay may be provided on a display panel.

From the foregoing discussion of apparatus and method for operating andcontrolling novel laundering apparatus and various components thereof,it will be apparent that numerous changes, variations, modifications andequivalents will now occur to those skilled in the art, which fallwithin the spirit and scope contemplated by the present invention.Accordingly, it is intended that the invention be limited only by thespirit and scope of the appended claims.

I claim:
 1. A method of operating a DC motor energized from an AC sourcecomprising the steps of:rectifying the output of the AC source toprovide a full wave rectified sinusoidal voltage; converting the fullwave rectified sinusoidal voltage into voltage pulses having a highfrequency with respect to the frequency of the full wave rectifiedsinusoidal voltage so as to provide an effective voltage to the motor;and limiting the voltage pulses to the time interval in each half cycleof the full wave rectified sinusoidal voltage during which the full waverectified sinusoidal voltage exceeds the effective voltage.
 2. Themethod as set forth in claim 1 further comprising the step of widthmodulating the voltage pulses to maintain a substantially constantcurrent in the DC motor throughout the time interval in each half cycleof the full wave rectified sinusoidal voltage during which the full waverectified sinusoidal voltage exceeds the effective voltage.
 3. A methodof operating an electronically commutated motor energized from an ACsource and having a stationary assembly including a plurality of windingstages adapted to be selectively commutated, and rotatable meansassociated with the stationary assembly in selective magnetic couplingrelation with the winding stages, the motor being responsive to acontrol circuit for controlling the current flow through a plurality ofcurrent paths each including at least one of the winding stages, themethod comprising:rectifying the AC voltage of the source to provide afull wave rectified sinusoidal voltage; generating pulses having a highfrequency with respect to the frequency of the full wave rectifiedsinusoidal voltage; commutating the winding stages by applying the fullwave rectified sinusoidal voltage thereto and causing the current pathsto become conductive in at least one preselected sequence; andcontrolling the conductivity of respective current paths as a functionof the width of the pulses when the current paths are sequentiallyrendered conductive.
 4. The method as set forth in claim 3 wherein thecontrolling step provides an effective voltage to the motor and themethod comprises the additional step of limiting the energization of themotor to a time interval in each half cycle of the full wave rectifiedsinusoidal voltage when the ratio of the effective voltage to the ACsource voltage has a selectively determined relationship.
 5. A circuitfor controlling the energization of an electrical load from an ACsource, comprising:a pair of DC lines; means for rectifying the ACoutput of the source to apply a DC voltage across said DC lines in theform of a full wave rectified sinusoidal voltage; means for chopping thefull wave rectified sinusoidal voltage to apply pulses to the load at afrequency which is high with respect to the frequency of the full waverectified sinusoidal voltage during the time interval when the full waverectified sinusoidal voltage exceeds the voltage across the load; andmeans connected to said chopping means for modulating the width of thepulses and for thereby maintaining the amplitude of the load currentbelow a predetermined level responsive to an externally derived signalrepresentative of the desired operation of the load.
 6. A circuit as setforth in claim 5 wherein said chopping means comprises a switchingtransistor connected in series between one of said DC lines and theload, said pulse width modulation means being connected to the base ofsaid transistor.
 7. A circuit for controlling the energization of anelectronically commutated motor from an AC source, the motor including astationary assembly having a plurality of winding stages associatedtherewith and adapted to be selectively commutated, and rotatable meansassociated with the stationary assembly in selective magnetic couplingrelation with the winding stages, the circuit comprising:a pair of DClines; means for rectifying the AC output of the source to apply a DCvoltage across said DC lines in the form of a full wave rectifiedsinusoidal voltage; means responsive to the angular position of therotatable assembly for deriving commutation signals; a plurality ofcurrent paths connected across said DC lines each including electroniccommutation means for connection in series with at least one of thewinding stages and responsive to the commutation signals to render saidcurrent paths conductive in sequence; means connected to saidcommutation means for chopping the full wave rectified sinusoidalvoltage in each of said conductive current paths so as to provide pulsesin said conductive current paths having a frequency which is high withrespect to the frequency of the full wave rectified sinusoidal voltageduring the time interval when the full wave rectified sinusoidal voltageexceeds the voltage across the electronically commutated motor; andmeans responsive to an externally derived signal representative of thedesired operation of the motor for modulating the width of the pulses.8. A circuit as set forth in claim 7 wherein the action of saidcommutation means produces an effective voltage and current in thewinding stages as said current paths become conductive, the pulse widthmodulating means comprisingmeans responsive to the effective current inthe winding stages for also modifying the externally derived signal tomaintain the effective current below a predetermined level.
 9. A circuitfor controlling an electronically commutated motor for use with a powersupply for supplying a full wave rectified sinusoidal voltage, theelectronically commutated motor including a stationary assembly having aplurality of winding stages adapted to be selectively commutated, androtatable means associated with the stationary assembly in selectivemagnetic coupling relation with the winding stages, the circuitcomprising:means for producing pulses of the full wave rectifiedsinusoidal voltage during a single continuous interval in each halfcycle of the full wave rectified sinusoidal voltage and applying them tothe winding stages in at least one preselected sequence thereby tocommutate the winding stages and rotate the rotatable means, the voltagepulses having a frequency which is high with respect to the frequency ofthe full wave rectified sinusoidal voltage; and means for widthmodulating the voltage pulses to produce substantially rectangularcurrent pulses flowing in the electronically commutated motor, each ofthe rectangular current pulses occurring during the single continuousinterval in each half cycle of the full wave rectified sinusoidalvoltage.
 10. The circuit as set forth in claim 9 wherein said widthmodulating means includes means for also adjusting the current flowingin the motor as a function of an input signal indicative of a desiredangular velocity of the rotating means.
 11. The circuit as set forth inclaim 9 wherein said voltage pulse producing and applying means includesswitching transistor means and filter means connected between saidswitching transistor means and the winding stages for producing themotor current at the output of said filter means.
 12. The circuit as setforth in claim 9 wherein said voltage pulses producing and applyingmeans includes means for also producing the pulses of the full waverectified sinusoidal voltage only during a predetermined time intervalin each half cycle of the full wave rectified sinusoidal voltage, theinitiating and terminating points respectively of each suchpredetermined time interval being spaced substantially equal phaseangles away from the initiating and terminating zero crossoversrespectively that define the corresponding half cycle of the full waverectified sinusoidal voltage.
 13. The circuit as set forth in claim 9wherein said voltage pulse producing and applying means comprises meansfor also limiting the production of the voltage pulses so that thesingle continuous interval in each half cycle of the full wave rectifiedsinusoidal voltage is the time interval during which the full waverectified sinusoidal voltage exceeds the voltage across the motor. 14.An electronically commutated motor system comprising:an electronicallycommutated motor including a stationary assembly having a plurality ofwinding stages associated therewith adapted to be selectivelycommutated, and rotatable means associated with said stationary assemblyin selective magnetic coupling relation with said winding stages; powersupply means for supplying a full wave rectified sinusoidal voltage;means for producing pulses of the full wave rectified sinusoidal voltageduring a single continuous interval in each half cycle of the full waverectified sinusoidal voltage and applying them to said winding stages inat least one preselected sequence thereby to commutate said windingstages and rotate said rotatable means, the voltage pulses having afrequency which is high with respect to the frequency of the full waverectified sinusoidal voltage; and means for width modulating the voltagepulses to produce substantially rectangular current pulses flowing insaid electronically commutated motor, each of the rectangular currentpulses occurring during the single continuous interval in each halfcycle of the full wave rectified sinusoidal voltage.
 15. Theelectronically commutated motor system as set forth in claim 14 whereinsaid width modulating means includes means for also adjusting thecurrent flowing in said motor as a function of an input signalindicative of a desired angular velocity of said rotatable means. 16.The electronically commutated motor system as set forth in claim 14wherein said voltage pulse producing and applying means includesswitching transistor means and filter means connected between saidswitching transistor means and said winding stages for producing themotor current at the output of said filter means.
 17. The electronicallycommutated motor system as set forth in claim 14 wherein said voltagepulse producing and applying means includes means for also producing thepulses of the full wave rectified sinusoidal voltage only during apredetermined time inverval in each half cycle of the full waverectified sinusoidal voltage, the initiating and terminating pointsrespectively of each such predetermined time interval being spacedsubstantially equal phase angles away from the initiating andterminating zero crossovers respectively that define the correspondinghalf cycle of the full wave rectified sinusoidal voltage.
 18. Theelectronically commutated motor system as set forth in claim 14 whereinsaid voltage pulse producing and applying means comprises means for alsolimiting the production of the voltage pulses so that the singlecontinuous interval in each half cycle of the full wave rectifiedsinusoidal voltage is the time interval during which the full waverectified sinusoidal voltage exceeds the voltage across said motor. 19.The electronically commutated motor system as set forth in claim 14wherein said voltage pulse producing and applying means comprises pairsof series connected electronic devices, each pair having a junctionpoint connected to each of said winding stages respectively, saidelectronic devices being able to be switched on in the at least onepreselected sequence, and means for switching the full wave rectifiedsinusoidal voltage at the high frequency across all of said pairs ofseries connected electronic devices in response to said width modulatingmeans.
 20. The electronically commutated motor system as set forth inclaim 14 wherein said voltage pulse producing and applying meanscomprises oscillator means, commutation circuit means, logic gate means,and pairs of series connected electronic devices each pair having ajunction point connected to each of the winding stages respectively,said electronic devices being enabled in the at least one preselectedsequence by said commutation circuit means through said logic gatemeans, said oscillator means switching said electronic devices which areenabled through said logic gate means at the frequency which is highwith respect to the full wave rectified sinusoidal voltage.
 21. Laundryapparatus comprising:means operable generally in a laundering mode foragitating fluid and fabrics to be laundered therein and operablegenerally in a spin mode for thereafter spinning the fabrics to effectcentrifugal displacement of fluid from the fabrics; an electronicallycommutated motor including a stationary assembly, a multi-stage windingarrangement associated with said stationary assembly and having aplurality of winding stages adapted to be commutated in a plurality ofpreselected sequences, and rotatable means rotatably associated withsaid stationary assembly and arranged in selective magnetic couplingrelation with said winding stages for driving said agitating andspinning means in the laundering mode operation and in the spin modeoperation thereof upon the commutation of said winding stages; powersupply means for supplying a full wave rectified sinusoidal voltage;means for producing pulses of the full wave rectified sinusoidal voltageduring a single continuous interval in each half cycle of the full waverectified sinusoidal voltage, for applying them to said winding stagesin one of the preselected sequences to commutate said winding stages andeffect the spin mode operation of said agitating and spinning means andfor applying the voltage pulses to said winding stages in both the onepreselected sequence and another preselected sequence to effect thelaundering mode operation of said agitating and spinning means, thevoltage pulses having a frequency which is high with respect to thefrequency of the full wave rectified sinusoidal voltage; and means forwidth modulating the voltage pulses to produce substantially rectangularcurrent pulses flowing in said electronically commutated motor, each ofthe rectangular current pulses occurring during the single continuousinterval in each half cycle of the full wave rectified sinusoidalvoltage.
 22. The laundry apparatus as set forth in claim 21 wherein saidwidth modulating means includes means for also adjusting the currentflowing in said motor as a function of an input signal indicative of adesired angular velocity of said rotatable means.
 23. The laundryapparatus as set forth in claim 21 wherein said voltage pulse producingand applying means includes switching transistor means and filter meansconnected between said switching transistor means and said windingstages for producing the motor current at the output of said filtermeans.
 24. The laundry apparatus as set forth in claim 21 wherein saidvoltage pulse producing and applying means includes means for alsoproducing the pulses of the full wave rectified sinusoidal voltage onlyduring a predetermined time interval in each half cycle of the full waverectified sinusoidal voltage.
 25. The laundry apparatus as set forth inclaim 21 wherein said voltage pulse producing and applying meanscomprises means for also limiting the production of the voltage pulsesso that the single continuous interval in each half cycle of the fullwave rectified sinusoidal voltage is the time interval during which thefull wave rectified sinusoidal voltage exceeds the voltage across saidmotor.
 26. The laundry apparatus as set forth in claim 21 wherein saidvoltage pulse producing and applying means comprises pairs of seriesconnected electronic devices, each pair having a junction pointconnected to each of said winding stages respectively, said electronicdevices being able to be switched on in each of the preselectedsequences, and means for switching the full wave rectified sinusoidalvoltage at the high frequency across all of said pairs of seriesconnected electronic devices in response to said width modulating means.27. The laundry apparatus as set forth in claim 21 wherein said voltagepulse producing and applying means comprises oscillator means,commutation circuit means, logic gate means, and pairs of seriesconnected electronic devices each pair having a junction point connectedto each of the winding stages respectively, said electronic devicesbeing enabled in each of the preselected sequences by said commutationcircuit means through said logic gate means, said oscillator meansswitching said electronic devices which are enabled through said logicgate means at the frequency which is high with respect to the full waverectified sinusoidal voltage.
 28. A method of operating a system havingan electronically commutated motor including a stationary assemblyhaving a plurality of winding stages adapted to be selectivelycommutated, and rotatable means associated with the stationary assemblyin selective magnetic coupling relation with the winding stages, powersupply means for supplying a full wave rectified sinusoidal voltage, andmeans for commutating the winding stages by applying a voltage theretoin at least one preselected sequence during successive commutationperiods thereby to rotate the rotatable means, the method comprising thesteps of:switching the full wave rectified sinusoidal voltage at afrequency which is high with respect to the frequency of the full waverectified sinusoidal voltage during a single continuous interval in eachhalf cycle of the full wave rectified sinusoidal voltage thereby toproduce the voltage applied by the commutating means in pulses; andwidth modulating the switching to width modulate the voltage pulses andto produce substantially rectangular current pulses flowing in theelectronically commutated motor, each such current pulse occurringduring the single continuous interval in each half cycle of the fullwave rectified sinusoidal voltage.
 29. The method as set forth in claim28 further comprising the step of enabling the switching only during apredetermined time interval in each half cycle of the full waverectified sinusoidal voltage, the initiating and terminating pointsrespectively of each such predetermined time interval being spacedsubstantially equal phase angles away from the initiating andterminating zero crossovers respectively that define the correspondinghalf cycle of the full wave rectified sinusoidal voltage.
 30. The methodas set forth in claim 28 further comprising the step of limiting theswitching so that the single continuous interval in each half cycle ofthe full wave rectified sinusoidal signal is the time interval duringwhich the full wave rectified sinusoidal voltage exceeds the voltageacross the motor.
 31. A method of operating an electronically commutatedmotor including a stationary assembly having a plurality of windingstages adapted to be selectively commutated, and rotatable meansassociated with the stationary assembly in selective magnetic couplingrelation with the winding stages, the motor being responsive to acontrol circuit having a plurality of current paths to the windingstages, the method comprising:rectifying an AC voltage to provide a fullwave rectified sinusoidal voltage; generating pulses having a highfrequency with respect to the frequency of the full wave rectifiedsinusoidal voltage; commutating the winding stages by applying a voltagethereto and causing the current paths to become conductive in at leastone preselected sequence; and switching the full wave rectifiedsinusoidal voltage in response to the high frequency pulses during thetime interval in each half cycle of the full wave rectified sinusoidalvoltage during which the full wave rectified sinusoidal voltage exceedsthe voltage across the motor thereby to produce the voltage applied bythe commutating means in pulses having a frequency which is high withrespect to the frequency of the full wave rectified sinusoidal voltage.32. The method as set forth in claim 31 further comprising the step ofwidth modulating the switching to width modulate the voltage pulses andto produce substantially rectangular current pulses flowing in theelectronically commutated motor, each such current pulse occupying thetime interval in each half cycle of the full wave rectified sinusoidalvoltage during which the full wave rectified sinusoidal voltage exceedsthe voltage across the motor.
 33. Laundry apparatus comprising:meansoperable generally in a laundering mode for agitating fluid and fabricsto be laundered therein and operable generally in a spin mode forthereafter spinning the fabrics to effect centrifugal displacement offluid from the fabrics; an electronically commutated motor including astationary assembly, a multi-stage winding arrangement associated withsaid stationary assembly and having a plurality of winding stagesadapted to be commutated in a plurality of preselected sequences, androtatable means rotatably associated with said stationary assembly andarranged in selective magnetic coupling relation with said windingstages for driving said agitating and spinning means in the launderingmode operation and in the spin mode operation thereof upon thecommutation of said winding stages; power supply means for supplying afull wave rectified sinusoidal voltage; means for switching the fullwave rectified sinusoidal voltage to produce voltage pulses during asingle continuous interval in each half cycle of the full wave rectifiedsinusoidal voltage, for filtering the voltage pulses and for applyingthe filtered voltage pulses to at least some of said winding stages inat least one of the preselected sequences to commutate said at leastsome winding stages and effect the laundering mode and the spin modeoperation of said agitating and spinning means, the voltage pulseshaving a frequency which is high with respect to the frequency of thefull wave rectified sinusoidal voltage; and means for width modulatingthe voltage pulses to produce substantially rectangular current pulsesflowing in said electronically commutated motor, each of the rectangularcurrent pulses occuring during the single continuous interval in eachhalf cycle of the full wave rectified sinusoidal voltage, and foradjusting the level of the rectangular current pulses in said motor as afunction of an input signal.
 34. Laundry apparatus as set forth in claim33 wherein said switching, filtering, and applying means includes aplurality of sets of electronic switching devices, each set having atleast one junction point connected to a corresponding one of said atleast some winding stages.
 35. Laundry apparatus comprising:meansoperable generally in a laundering mode for agitating fluid and fabricsto be laundered therein and operable generally in a spin mode forthereafter spinning the fabrics to effect centrifugal displacement offluid from the fabrics; an electronically commutated motor including astationary assembly, a multi-stage winding arrangement associated withsaid stationary assembly and having a plurality of winding stagesadapted to be commutated in a plurality of preselected sequences, androtatable means rotatably associated with said stationary assembly andarranged in selective magnetic coupling relation with said windingstages for driving said agitating and spinning means in the launderingmode operation and in the spin mode operation thereof upon thecommutation of said winding stages; power supply means for supplying afull wave rectified sinusoidal voltage; means for producing pulses ofthe full wave rectified sinusoidal voltage which are confined to asingle continuous interval in each half cycle of the full wave rectifiedsinusoidal voltage during which the full wave rectified sinusoidalvoltage exceeds the voltage across said motor, for applying them to atleast some of said winding stages in one of the preselected sequences tocommutate said at least some winding stages and effect the spin modeoperation of said agitating and spinning means and for applying thevoltage pulses to at least some of said winding stages in both the onepreselected sequence and another preselected sequence to effect thelaundering mode operation of said agitating and spinning means, thevoltage pulses having a frequency which is high with respect to thefrequency of the full wave rectified sinusoidal voltage; and means forwidth modulating the voltage pulses to produce substantially rectangularcurrent pulses flowing in said electronically commutated motor, each ofthe rectangular current pulses occurring during the single continuousinterval in each half cycle of the full wave rectified sinusoidalvoltage, and for adjusting the current in said motor as a function of aninput signal indicative of a desired angular velocity of said rotatablemeans.
 36. The laundry apparatus as set forth in claim 35 wherein saidvoltage pulse producing and applying means includes switching transistormeans and filter means connected between said switching transistor meansand said winding stages for producing the motor current at the output ofsaid filter means.
 37. Laundry apparatus comprising:means operablegenerally in a laundering mode for agitating fluid and fabrics to belaundered therein and operable generally in a spin mode for thereafterspinning the fabrics to effect centrifugal displacement of fluid fromthe fabrics; an electronically commutated motor including a stationaryassembly, a multi-stage winding arrangement associated with saidstationary assembly and having a plurality of winding stages adapted tobe commutated in a plurality of preselected sequences, and rotatablemeans rotatably associated with said stationary assembly and arranged inselective magnetic coupling relation with said winding stages fordriving said agitating and spinning means in the laundering modeoperation and in the spin mode operation thereof upon the commutation ofsaid winding stages; power supply means for supplying a full waverectified sinusoidal voltage; a plurality of sets of electronic devices,each set having at least one junction point connected to at least someof said winding stages, respectively, said electronic devices being ableto be switched on in at least some of the preselected sequences; meansfor switching the full wave rectified sinusoidal voltage across all ofsaid sets of electronic devices; and means connected to said switchingmeans for causing pulses of the full wave rectified sinusoidal voltageto be produced by said switching means, the voltage pulses having afrequency which is high with respect to the frequency of the full waverectified sinusoidal voltage, and for width modulating the voltagepulses to produce substantially rectangular current pulses flowing insaid electronically commutated motor, each of the rectangular currentpulses occurring during a single continuous interval in each half cycleof the full wave rectified sinusoidal voltage.
 38. Laundry apparatus asset forth in claim 37 wherein said voltage pulse causing and widthmodulating means includes oscillator means, means for sensing thecurrent in said motor, and pulse width modulating means having inputsconnected to said oscillator means and to said sensing means, and anoutput connected to control said switching means.
 39. Laundry apparatusas set forth in claim 37 further comprising filtering means connectedbetween said switching means and said sets of electronic devices. 40.Laundry apparatus comprising:means operable generally in a launderingmode for agitating fluid and fabrics to be laundered therein andoperable generally in a spin mode for thereafter spinning the fabrics toeffect centrifugal displacement of fluid from the fabrics; anelectronically commutated motor including a stationary assembly, amulti-stage winding arrangement associated with said stationary assemblyand having a plurality of winding stages adapted to be commutated in aplurality of preselected sequences, and rotatable means rotatablyassociated with said stationary assembly and arranged in selectivemagnetic coupling relation with said winding stages for driving saidagitating and spinning means in the laundering mode operation and in thespin mode operation thereof upon the commutation of said winding stages;first and second DC lines; power supply means for supplying a full waverectified sinusoidal voltage across said first and second DC lines;means responsive to the angular position of said rotatable means forderiving commutation signals; a plurality of current paths connected toat least one of said DC lines, each of said current paths includingelectronic commutation means for connection in series with at least oneof said winding stages and responsive to the commutation signals formaking said current paths conductive in one of the preselected sequencesto commutate at least some of said winding stages to effect the spinmode operation of said agitating and spinning means and for making saidcurrent paths conductive in both the one preselected sequence andanother preselected sequence to effect the laundering mode operation ofsaid agitating and spinning means; and means connected to saidcommutation means for chopping the full wave rectified sinusoidalvoltage in each of said conductive current paths to provide voltagepulses in said conductive current paths having a frequency which is highwith respect to the frequency of the full wave rectified sinusoidalvoltage and for width modulating the voltage pulses to producesubstantially rectangular current pulses respectively flowing in saidelectronically commutated motor in a single continuous interval in eachof at least some of the half cycles of the full wave rectifiedsinusoidal voltage.
 41. Laundry apparatus as set forth in claim 40wherein at least one of said electronic commutation means includes logicgate means and a plurality of transistors connected between said atleast one winding stage and at least one of said first and second DClines, said logic gate means coupling said means for derivingcommutation signals to at least one of said transistors.
 42. Laundryapparatus as set forth in claim 41 wherein said chopping and widthmodulating means is connected to said logic gate means.
 43. Laundryapparatus as set forth in claim 41 wherein said chopping and widthmodulating means is connected to said logic gate means to disable saidlogic gate means at the frequency which is high with respect to the fullwave rectified sinusoidal voltage thereby causing at least one at a timeof said transistors to be switched at the high frequency, said meansresponsive to the angular position of said rotatable means for derivingcommutation signals including means for selecting in at least one of thepreselected sequences each of said transistors which is to be switchedat the high frequency.
 44. Laundry apparatus as set forth in claim 40wherein said chopping and width modulating means includes means for alsoadjusting the current flowing in said motor as a function of an inputsignal indicative of a desired angular velocity of said rotatable means.45. Laundry apparatus comprising:means operable generally in alaundering mode for agitating fluid and fabrics to be laundered thereinand operable generally in a spin mode for thereafter spinning thefabrics to effect centrifugal displacement of fluid from the fabrics; anelectronically commutated motor including a stationary assembly, amulti-stage winding arrangement associated with said stationary assemblyand having a plurality of winding stages adapted to be commutated in aplurality of preselected sequences, and rotatable means rotatablyassociated with said stationary assembly and arranged in selectivemagnetic coupling relation with said winding stages for driving saidagitating and spinning means in the laundering mode operation and in thespin mode operation thereof upon the commutation of said winding stages;power supply means for supplying a full wave rectified sinusoidalvoltage; means for converting the full wave rectified sinusoidal voltageinto voltage pulses having a high frequency with respect to thefrequency of the full wave rectified sinusoidal voltage so as to providean effective voltage to said electronically commutated motor, thevoltage pulses being confined by said converting means to a singlecontinuous time interval in each half cycle of the full wave rectifiedsinusoidal voltage; and means for width modulating the voltage pulses tomaintain a substantially constant current in said electronicallycommutated motor throughout the single continuous time interval. 46.Laundry apparatus as set forth in claim 45 wherein said means forconverting includes means for limiting the voltage pulses to a timeinterval in each half cycle of the full wave rectified sinusoidalvoltage during which the full wave rectified sinusoidal voltage has aselectively determined relationship to the effective voltage. 47.Laundry apparatus as set forth in claim 45 wherein said width modulatingmeans includes means for also adjusting the current flowing in saidmotor as a function of an input signal indicative of a desired angularvelocity of said rotatable means.
 48. Laundry apparatus comprising:meansoperable generally in a laundering mode for agitating fluid and fabricsto be laundered therein and operable generally in a spin mode forthereafter spinning the fabrics to effect centrifugal displacement offluid from the fabrics; an electronically commutated motor including astationary assembly, a multi-stage winding arrangement associated withsaid stationary assembly and having a plurality of winding stagesadapted to be commutated in a plurality of preselected sequences, androtatable means rotatably associated with said stationary assembly andarranged in selective magnetic coupling relation with said windingstages for driving said agitating and spinning means in the launderingmode operation and in the spin mode operation thereof upon thecommutation of said winding stages; means for rectifying an AC voltageto provide a full wave rectified sinusoidal voltage; means forgenerating pulses having a high frequency with respect to the frequencyof the full wave rectified sinusoidal voltage; means for commutatingsaid winding stages by applying a voltage thereto in at least onepreselected sequence; means for switching the full wave rectifiedsinusoidal voltage in response to the high frequency pulses during asingle continuous interval in each half cycle of the full wave rectifiedsinusoidal voltage thereby to produce the voltage applied by thecommutating means in pulses having a frequency which is high withrespect to the frequency of the full wave rectified sinusoidal voltage;and means for width modulating the switching to width modulate thevoltage pulses and to produce a current flowing in the electronicallycommutated motor which is substantially rectangular pulses, each suchcurrent pulse occupying the single continuous interval in each halfcycle of the full wave rectified sinusoidal voltage.
 49. The laundryapparatus as set forth in claim 48 further comprising filter meansconnected between said switching means and said commutating means. 50.The laundry apparatus as set forth in claim 48 wherein said widthmodulating means includes means for also adjusting the current flowingin said electronically commutated motor as a function of an input signalindicative of a desired angular velocity of said rotating means.